Refactor account card title and layout styles for improved UI consistency

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

@@ -2,7 +2,7 @@
 
 <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>
+        <h3 class="card-title mb-3 mt-0">@Account.Name</h3>
         <div class="@(Account.TotalBalance >= 0 ? "amount-positive" : "amount-negative") fs-4">
             @($"{Account.TotalBalance:N2} €")
         </div>

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

@@ -5,7 +5,6 @@
         <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">

src/Duempelkas.App/Pages/Accounts/AccountDetail.razor

@@ -16,11 +16,8 @@
     else
     {
         <div class="d-flex align-items-center gap-2 mb-3">
-            <button class="btn btn-outline-secondary btn-sm flex-shrink-0" @onclick="NavigateBack">
-                <i class="bi bi-arrow-left"></i> Zurück
-            </button>
             <div class="d-flex align-items-center flex-grow-1" style="min-width: 0;">
-                <h2 class="mb-0" style="overflow: hidden; text-overflow: ellipsis; white-space: nowrap;">
+                <h2 class="mb-0 mt-0" style="overflow: hidden; text-overflow: ellipsis; white-space: nowrap;">
                     @account.Name
                     <button class="btn-edit-pen" @onclick="() => showEditName = true" title="Name bearbeiten"><i class="bi bi-pencil"></i></button>
                 </h2>
@@ -29,7 +26,7 @@
 
         @if (balance != null)
         {
-            <div class="summary-section mb-3">
+            <div class="summary-section">
                 <div class="summary-flex">
                     <div>
                         <small class="text-muted">Saldo</small>
@@ -50,7 +47,7 @@
 
             @if (showCurrentYearOnly)
             {
-                <div class="summary-section mb-3">
+                <div class="summary-section">
                     <div class="summary-flex">
                         <div>
                             <small class="text-muted">Übertrag von @(DateTime.Now.Year - 1)</small>
@@ -73,6 +70,9 @@
         }
 
         <div class="d-flex align-items-center gap-2 mb-3 py-3 flex-wrap">
+            <button class="btn btn-secondary btn-sm" @onclick="NavigateBack">
+                <i class="bi bi-arrow-left"></i> Zurück
+            </button>
             <button class="btn btn-success btn-sm" @onclick="() => showAddEntry = true">
                 <i class="bi bi-plus-lg"></i> Eintrag
             </button>