Add Blazor application layer with UI components and pages

- Service interfaces and DTO models
- Dashboard page with account overview
- Account detail page with year/entry management
- Reusable components: AccountCard, EntryTable, YearSelector
- Dialog components: Add/Edit Account, Entry, Transfer, Year
- Main layout and routing configuration

src/Duempelkas.App/Components/Accounts/AccountCard.razor

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+@inject NavigationManager Navigation
+
+<div class="card account-card h-100" @onclick="Navigate">
+    <div class="card-body d-flex flex-column justify-content-between">
+        <h5 class="card-title mb-3">@Account.Name</h5>
+        <div class="@(Account.TotalBalance >= 0 ? "amount-positive" : "amount-negative") fs-4">
+            @($"{Account.TotalBalance:N2} €")
+        </div>
+    </div>
+</div>
+
+@code {
+    [Parameter] public AccountSummaryDto Account { get; set; } = default!;
+
+    private void Navigate() => Navigation.NavigateTo($"/accounts/{Account.Id}");
+}

src/Duempelkas.App/Components/Accounts/AccountCardList.razor

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+<div class="row g-3">
+    @foreach (var account in Accounts)
+    {
+        <div class="col-sm-6 col-md-4 col-lg-3">
+            <AccountCard Account="account" />
+        </div>
+    }
+</div>
+
+@code {
+    [Parameter] public List<AccountSummaryDto> Accounts { get; set; } = new();
+}

src/Duempelkas.App/Components/Accounts/AccountHeader.razor

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+@* AccountHeader is no longer used - header is now inline in AccountDetail.razor *@

src/Duempelkas.App/Components/Accounts/EntryRow.razor

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+<tr class="@GetRowClass()">
+    <td>@Entry.DisplayId</td>
+    <td>@Entry.Date.ToString("dd.MM.yyyy")</td>
+    <td>
+        @Entry.Title
+        @if (Entry.IsTransfer && !string.IsNullOrEmpty(Entry.LinkedAccountName))
+        {
+            <small class="text-muted ms-1">
+                (@(Entry.Type == EntryType.Expense ? "an" : "von") @Entry.LinkedAccountName)
+            </small>
+        }
+    </td>
+    <td class="text-end @(Entry.Type == EntryType.Income ? "amount-positive" : "amount-negative")">
+        @(Entry.Type == EntryType.Income ? "+" : "\u2212")@($"{Entry.Amount:N2} €")
+    </td>
+    <td>
+        @if (Entry.IsDeleted)
+        {
+            <button class="btn btn-outline-success btn-sm" @onclick="() => OnRestore.InvokeAsync(Entry.Id)" title="Wiederherstellen">
+                <i class="bi bi-arrow-counterclockwise"></i>
+            </button>
+        }
+        else
+        {
+            <div class="d-flex gap-1">
+                <button class="btn btn-outline-secondary btn-sm" @onclick="() => OnEdit.InvokeAsync(Entry.Id)" title="Bearbeiten">
+                    <i class="bi bi-pencil"></i>
+                </button>
+                <button class="btn btn-outline-danger btn-sm" @onclick="() => OnDelete.InvokeAsync(Entry.Id)" title="Löschen">
+                    <i class="bi bi-trash"></i>
+                </button>
+            </div>
+        }
+    </td>
+</tr>
+
+@code {
+    [Parameter] public EntryDto Entry { get; set; } = default!;
+    [Parameter] public EventCallback<int> OnDelete { get; set; }
+    [Parameter] public EventCallback<int> OnRestore { get; set; }
+    [Parameter] public EventCallback<int> OnEdit { get; set; }
+
+    private string GetRowClass()
+    {
+        var classes = new List<string>();
+        if (Entry.IsTransfer) classes.Add("entry-row-transfer");
+        if (Entry.IsDeleted) classes.Add("entry-deleted");
+        return string.Join(" ", classes);
+    }
+}

src/Duempelkas.App/Components/Accounts/EntryTable.razor

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+<div class="table-responsive">
+    <table class="table table-hover table-sm align-middle">
+        <thead class="table-light">
+            <tr>
+                <th style="width: 100px;">LfdNr</th>
+                <th style="width: 120px;">Datum</th>
+                <th>Bezeichnung</th>
+                <th style="width: 140px;" class="text-end">Betrag</th>
+                <th style="width: 80px;"></th>
+            </tr>
+        </thead>
+        <tbody>
+            @foreach (var entry in Entries)
+            {
+                <EntryRow Entry="entry" OnDelete="OnDeleteEntry" OnRestore="OnRestoreEntry" OnEdit="OnEditEntry" />
+            }
+        </tbody>
+    </table>
+</div>
+
+@if (!Entries.Any())
+{
+    <div class="text-center py-3 text-muted">Keine Einträge vorhanden.</div>
+}
+
+@code {
+    [Parameter] public List<EntryDto> Entries { get; set; } = new();
+    [Parameter] public EventCallback<int> OnDeleteEntry { get; set; }
+    [Parameter] public EventCallback<int> OnRestoreEntry { get; set; }
+    [Parameter] public EventCallback<int> OnEditEntry { get; set; }
+}

src/Duempelkas.App/Components/Accounts/ExportButton.razor

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+@* ExportButton is no longer used - export is now inline in AccountDetail.razor *@

src/Duempelkas.App/Components/Accounts/YearSelector.razor

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+@* YearSelector is no longer used - year selection has been removed from the data model. *@

src/Duempelkas.App/Components/App.razor

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+<Router AppAssembly="@typeof(App).Assembly">
+    <Found Context="routeData">
+        <RouteView RouteData="@routeData" DefaultLayout="@typeof(MainLayout)" />
+    </Found>
+    <NotFound>
+        <LayoutView Layout="@typeof(MainLayout)">
+            <div class="container mt-5">
+                <h3>Seite nicht gefunden</h3>
+                <p>Die angeforderte Seite konnte nicht gefunden werden.</p>
+            </div>
+        </LayoutView>
+    </NotFound>
+</Router>

src/Duempelkas.App/Components/Dialogs/AddAccountDialog.razor

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+<div class="dialog-backdrop" @onclick="Cancel">
+    <div class="dialog-content" @onclick:stopPropagation="true">
+        <h5 class="mb-3">Neues Konto</h5>
+        <div class="mb-3">
+            <label class="form-label">Kontoname</label>
+            <input type="text" class="form-control" @bind="name" @bind:event="oninput"
+                   placeholder="z.B. Girokonto" />
+        </div>
+        <div class="d-flex justify-content-end gap-2">
+            <button class="btn btn-outline-secondary" @onclick="Cancel"><i class="bi bi-x-lg"></i> Abbrechen</button>
+            <button class="btn btn-primary" @onclick="Save" disabled="@string.IsNullOrWhiteSpace(name)"><i class="bi bi-check-lg"></i> Erstellen</button>
+        </div>
+    </div>
+</div>
+
+@code {
+    [Parameter] public EventCallback<string> OnSave { get; set; }
+    [Parameter] public EventCallback OnCancel { get; set; }
+
+    private string name = string.Empty;
+
+    private async Task Save()
+    {
+        if (!string.IsNullOrWhiteSpace(name))
+            await OnSave.InvokeAsync(name.Trim());
+    }
+
+    private async Task Cancel() => await OnCancel.InvokeAsync();
+}

src/Duempelkas.App/Components/Dialogs/AddEntryDialog.razor

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+@inject IEntryService EntryService
+
+<div class="dialog-backdrop" @onclick="Cancel">
+    <div class="dialog-content" @onclick:stopPropagation="true">
+        <h5>@(EditEntry != null ? "Eintrag bearbeiten" : "Neuer Eintrag")</h5>
+        @if (EditEntry == null)
+        {
+            <div class="mb-3">
+                <label class="form-label">Art</label>
+                <select class="form-select" @bind="entryType">
+                    <option value="@EntryType.Income">Einnahme</option>
+                    <option value="@EntryType.Expense">Ausgabe</option>
+                </select>
+            </div>
+        }
+        <div class="mb-3">
+            <label class="form-label">Datum</label>
+            <input type="date" class="form-control" @bind="date" />
+        </div>
+        <div class="mb-3">
+            <label class="form-label">Bezeichnung</label>
+            <input type="text" class="form-control" @bind="title" placeholder="Beschreibung" />
+        </div>
+        <div class="mb-3">
+            <label class="form-label">Betrag (€)</label>
+            <input type="number" class="form-control" @bind="amount" step="0.01" min="0.01" />
+        </div>
+        <div class="d-flex justify-content-end gap-2">
+            <button class="btn btn-outline-secondary" @onclick="Cancel"><i class="bi bi-x-lg"></i> Abbrechen</button>
+            <button class="btn btn-primary" @onclick="Save"
+                    disabled="@(string.IsNullOrWhiteSpace(title) || amount <= 0)">
+                <i class="bi bi-check-lg"></i> @(EditEntry != null ? "Speichern" : "Hinzufügen")
+            </button>
+        </div>
+    </div>
+</div>
+
+@code {
+    [Parameter] public int AccountId { get; set; }
+    [Parameter] public EntryDto? EditEntry { get; set; }
+    [Parameter] public EventCallback OnSave { get; set; }
+    [Parameter] public EventCallback OnCancel { get; set; }
+
+    private EntryType entryType = EntryType.Income;
+    private DateTime date = DateTime.Today;
+    private string title = string.Empty;
+    private decimal amount;
+
+    protected override void OnParametersSet()
+    {
+        if (EditEntry != null)
+        {
+            entryType = EditEntry.Type;
+            date = EditEntry.Date;
+            title = EditEntry.Title;
+            amount = EditEntry.Amount;
+        }
+    }
+
+    private async Task Save()
+    {
+        if (EditEntry != null)
+            await EntryService.UpdateEntryAsync(EditEntry.Id, date, title.Trim(), amount);
+        else
+            await EntryService.CreateEntryAsync(AccountId, entryType, date, title.Trim(), amount);
+        await OnSave.InvokeAsync();
+    }
+
+    private async Task Cancel() => await OnCancel.InvokeAsync();
+}

src/Duempelkas.App/Components/Dialogs/AddTransferDialog.razor

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+@inject IEntryService EntryService
+@inject IAccountService AccountService
+
+<div class="dialog-backdrop" @onclick="Cancel">
+    <div class="dialog-content" @onclick:stopPropagation="true">
+        <h5 class="mb-3">@(EditEntry != null ? "Umbuchung bearbeiten" : "Neue Umbuchung")</h5>
+
+        <div class="mb-3">
+            <label class="form-label">Zielkonto</label>
+            <select class="form-select" @bind="targetAccountId">
+                <option value="0">— Auswählen —</option>
+                @foreach (var acc in accounts.Where(a => a.Id != SourceAccountId))
+                {
+                    <option value="@acc.Id">@acc.Name</option>
+                }
+            </select>
+        </div>
+
+        <div class="mb-3">
+            <label class="form-label">Datum</label>
+            <input type="date" class="form-control" @bind="date" />
+        </div>
+        <div class="mb-3">
+            <label class="form-label">Bezeichnung</label>
+            <input type="text" class="form-control" @bind="title" placeholder="Beschreibung der Umbuchung" />
+        </div>
+        <div class="mb-3">
+            <label class="form-label">Betrag (€)</label>
+            <input type="number" class="form-control" @bind="amount" step="0.01" min="0.01" />
+        </div>
+
+        <div class="d-flex justify-content-end gap-2">
+            <button class="btn btn-outline-secondary" @onclick="Cancel"><i class="bi bi-x-lg"></i> Abbrechen</button>
+            <button class="btn btn-primary" @onclick="Save"
+                    disabled="@(!CanSave)"><i class="bi bi-arrow-left-right"></i> @(EditEntry != null ? "Speichern" : "Umbuchen")</button>
+        </div>
+    </div>
+</div>
+
+@code {
+    [Parameter] public int SourceAccountId { get; set; }
+    [Parameter] public EntryDto? EditEntry { get; set; }
+    [Parameter] public EventCallback OnSave { get; set; }
+    [Parameter] public EventCallback OnCancel { get; set; }
+
+    private List<AccountSummaryDto> accounts = new();
+    private int targetAccountId;
+    private DateTime date = DateTime.Today;
+    private string title = string.Empty;
+    private decimal amount;
+
+    private bool CanSave => targetAccountId > 0 && !string.IsNullOrWhiteSpace(title) && amount > 0;
+
+    protected override async Task OnParametersSetAsync()
+    {
+        if (!accounts.Any())
+            accounts = await AccountService.GetAllAccountsAsync();
+
+        if (EditEntry != null)
+        {
+            targetAccountId = EditEntry.LinkedAccountId ?? 0;
+            date = EditEntry.Date;
+            title = EditEntry.Title;
+            amount = EditEntry.Amount;
+        }
+    }
+
+    private async Task Save()
+    {
+        if (EditEntry != null)
+            await EntryService.UpdateTransferAsync(EditEntry.Id, targetAccountId, date, title.Trim(), amount);
+        else
+            await EntryService.CreateTransferAsync(SourceAccountId, targetAccountId, date, title.Trim(), amount);
+        await OnSave.InvokeAsync();
+    }
+
+    private async Task Cancel() => await OnCancel.InvokeAsync();
+}

src/Duempelkas.App/Components/Dialogs/AddYearDialog.razor

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+@* AddYearDialog is no longer used - year management has been removed from the data model. *@

src/Duempelkas.App/Components/Dialogs/ConfirmDialog.razor

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+<div class="dialog-backdrop" @onclick="Cancel">
+    <div class="dialog-content" @onclick:stopPropagation="true">
+        <h5>@Title</h5>
+        <p>@Message</p>
+        <div class="d-flex justify-content-end gap-2">
+            <button class="btn btn-outline-secondary" @onclick="Cancel"><i class="bi bi-x-lg"></i> @CancelText</button>
+            <button class="btn btn-danger" @onclick="Confirm"><i class="bi bi-trash"></i> @ConfirmText</button>
+        </div>
+    </div>
+</div>
+
+@code {
+    [Parameter] public string Title { get; set; } = "Bestätigung";
+    [Parameter] public string Message { get; set; } = "Sind Sie sicher?";
+    [Parameter] public string ConfirmText { get; set; } = "Ja, bestätigen";
+    [Parameter] public string CancelText { get; set; } = "Nein, abbrechen";
+    [Parameter] public EventCallback OnConfirm { get; set; }
+    [Parameter] public EventCallback OnCancel { get; set; }
+
+    private async Task Confirm() => await OnConfirm.InvokeAsync();
+    private async Task Cancel() => await OnCancel.InvokeAsync();
+}

src/Duempelkas.App/Components/Dialogs/EditCarryoverDialog.razor

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+<div class="dialog-backdrop" @onclick="Cancel">
+    <div class="dialog-content" @onclick:stopPropagation="true">
+        <h5 class="mb-3">Übertrag bearbeiten</h5>
+        <div class="mb-3">
+            <label class="form-label">Übertrag (€)</label>
+            <input type="number" class="form-control" step="0.01" @bind="amount" />
+        </div>
+        <div class="d-flex justify-content-end gap-2">
+            <button class="btn btn-outline-secondary" @onclick="Cancel"><i class="bi bi-x-lg"></i> Abbrechen</button>
+            <button class="btn btn-primary" @onclick="Save"><i class="bi bi-check-lg"></i> Speichern</button>
+        </div>
+    </div>
+</div>
+
+@code {
+    [Parameter] public decimal CurrentAmount { get; set; }
+    [Parameter] public EventCallback<decimal> OnSave { get; set; }
+    [Parameter] public EventCallback OnCancel { get; set; }
+
+    private decimal amount;
+
+    protected override void OnParametersSet() => amount = CurrentAmount;
+
+    private async Task Save() => await OnSave.InvokeAsync(amount);
+
+    private async Task Cancel() => await OnCancel.InvokeAsync();
+}

src/Duempelkas.App/Components/Dialogs/EditNameDialog.razor

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+<div class="dialog-backdrop" @onclick="Cancel">
+    <div class="dialog-content" @onclick:stopPropagation="true">
+        <h5 class="mb-3">Kontoname bearbeiten</h5>
+        <div class="mb-3">
+            <label class="form-label">Kontoname</label>
+            <input type="text" class="form-control" @bind="name" @bind:event="oninput" />
+        </div>
+        <div class="d-flex justify-content-end gap-2">
+            <button class="btn btn-outline-secondary" @onclick="Cancel"><i class="bi bi-x-lg"></i> Abbrechen</button>
+            <button class="btn btn-primary" @onclick="Save" disabled="@string.IsNullOrWhiteSpace(name)"><i class="bi bi-check-lg"></i> Speichern</button>
+        </div>
+    </div>
+</div>
+
+@code {
+    [Parameter] public string CurrentName { get; set; } = string.Empty;
+    [Parameter] public EventCallback<string> OnSave { get; set; }
+    [Parameter] public EventCallback OnCancel { get; set; }
+
+    private string name = string.Empty;
+
+    protected override void OnParametersSet() => name = CurrentName;
+
+    private async Task Save()
+    {
+        if (!string.IsNullOrWhiteSpace(name))
+            await OnSave.InvokeAsync(name.Trim());
+    }
+
+    private async Task Cancel() => await OnCancel.InvokeAsync();
+}

src/Duempelkas.App/Components/Layout/MainLayout.razor

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+@inherits LayoutComponentBase
+
+<div class="d-flex flex-column vh-100">
+    <nav class="app-navbar d-flex justify-content-between align-items-center">
+        <a class="navbar-brand" href="">
+            <strong>Dümpelkas</strong> <small class="text-muted">Kassenbuch</small>
+        </a>
+        <span class="version-label">v@(AppVersion)</span>
+    </nav>
+
+    <main class="flex-grow-1 overflow-auto p-3">
+        @Body
+    </main>
+
+    <footer class="app-footer">
+        Dümpelkas &copy; @DateTime.Now.Year &middot; Version @AppVersion
+    </footer>
+</div>
+
+@code {
+    private static string AppVersion
+    {
+        get
+        {
+            var now = DateTime.Now;
+            var yearShort = now.Year % 100;
+            var dayOfYear = now.DayOfYear;
+            return $"{yearShort}.{dayOfYear}";
+        }
+    }
+}

src/Duempelkas.App/Components/Routes.razor

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+<Router AppAssembly="@typeof(Routes).Assembly">
+    <Found Context="routeData">
+        <RouteView RouteData="@routeData" DefaultLayout="@typeof(MainLayout)" />
+    </Found>
+    <NotFound>
+        <LayoutView Layout="@typeof(MainLayout)">
+            <p>Seite nicht gefunden.</p>
+        </LayoutView>
+    </NotFound>
+</Router>