feat(usability): preserve reporting year and locate outside-period bookings (U04)

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

@@ -25,9 +25,17 @@
             <input type="number" class="form-control no-spinner" @bind="amount" step="0.01" min="0.01" />
         </div>
 
+        @if (OutsideYear)
+        {
+            <div class="alert alert-warning" role="status">
+                Datum @date.ToString("dd.MM.yyyy"): Diese Buchung liegt außerhalb von Jahr @ContextYear und wird dort nicht angezeigt.
+                <label><input type="checkbox" checked="@(confirmDifferentYear && confirmedYear == date.Year)" @onchange="e => { confirmDifferentYear = e.Value is true; confirmedYear = date.Year; }" /> Ich möchte die Buchung im Jahr @date.Year speichern.</label>
+            </div>
+        }
+
         <div class="d-flex justify-content-end gap-2">
             <button class="btn btn-success" @onclick="Save"
-                    disabled="@(!CanSave)"><i class="bi bi-arrow-left-right"></i> @(EditEntry != null ? "Speichern" : "Hinzufügen")</button>
+                    disabled="@(!CanSave || (OutsideYear && (!confirmDifferentYear || confirmedYear != date.Year)))"><i class="bi bi-arrow-left-right"></i> @(EditEntry != null ? "Speichern" : "Hinzufügen")</button>
             <button class="btn btn-outline-secondary" @onclick="Cancel"><i class="bi bi-x-lg"></i> Abbrechen</button>
         </div>
     </div>