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/Services/IEntryService.cs

@@ -0,0 +1,15 @@
+using Duempelkas.App.Services.Models;
+using Duempelkas.Domain.Enums;
+
+namespace Duempelkas.App.Services;
+
+public interface IEntryService
+{
+    Task<List<EntryDto>> GetEntriesAsync(int accountId, bool currentYearOnly);
+    Task<EntryDto> CreateEntryAsync(int accountId, EntryType type, DateTime date, string title, decimal amount);
+    Task CreateTransferAsync(int sourceAccountId, int targetAccountId, DateTime date, string title, decimal amount);
+    Task DeleteEntryAsync(int entryId);
+    Task RestoreEntryAsync(int entryId);
+    Task UpdateEntryAsync(int entryId, DateTime date, string title, decimal amount);
+    Task UpdateTransferAsync(int entryId, int newLinkedAccountId, DateTime date, string title, decimal amount);
+}