fix: single keyboard Done toolbar on Complete Task (closes gitea#5)

The actualCost TextField and the notes TextEditor each had their own
`.keyboardDismissToolbar()` modifier, which installs a separate
`ToolbarItemGroup(placement: .keyboard)`. SwiftUI accumulates these
on the responder chain, so focusing any field rendered two "Done"
buttons stacked above the keyboard (issue screenshot in gitea#5).

Move the modifier up to the Form root so exactly one keyboard
toolbar is registered for the entire screen, matching the pattern
already used by `TaskFormView`.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

iosApp/iosApp/Task/CompleteTaskView.swift

@@ -120,7 +120,6 @@ struct CompleteTaskView: View {
                                     .foregroundStyle(.secondary)
                             }
                             .padding(.leading, 12)
-                            .keyboardDismissToolbar()
                             .accessibilityIdentifier(AccessibilityIdentifiers.Task.actualCostField)
                     } label: {
                         Label(L10n.Tasks.actualCost, systemImage: "dollarsign.circle")
@@ -142,7 +141,6 @@ struct CompleteTaskView: View {
                         TextEditor(text: $notes)
                             .frame(minHeight: 100)
                             .scrollContentBackground(.hidden)
-                            .keyboardDismissToolbar()
                             .accessibilityIdentifier(AccessibilityIdentifiers.Task.notesField)
                     }
                 } footer: {
@@ -289,6 +287,12 @@ struct CompleteTaskView: View {
             .background(WarmGradientBackground())
             .navigationTitle(L10n.Tasks.completeTask)
             .navigationBarTitleDisplayMode(.inline)
+            // ONE keyboard "Done" toolbar at the form root — per-field
+            // `.keyboardDismissToolbar()` modifiers each install a
+            // separate `ToolbarItemGroup(placement: .keyboard)`, and
+            // SwiftUI stacks them on the responder chain so any focused
+            // field renders multiple Done buttons side-by-side (issue #5).
+            .keyboardDismissToolbar()
             .toolbar {
                 ToolbarItem(placement: .cancellationAction) {
                     Button(L10n.Common.cancel) {