Add keyboard dismiss toolbar for iOS numeric and multi-line fields

Creates a reusable KeyboardDismissToolbar view modifier that adds a
"Done" button to dismiss keyboards that don't have a return key.
Applied to all numeric keyboards (numberPad, decimalPad, phonePad)
and multi-line text inputs (TextEditor, TextField with axis: .vertical).

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

iosApp/iosApp/Task/TaskFormView.swift

@@ -188,6 +188,7 @@ struct TaskFormView: View {
                         TextField(L10n.Tasks.descriptionOptional, text: $description, axis: .vertical)
                             .lineLimit(3...6)
                             .focused($focusedField, equals: .description)
+                            .keyboardDismissToolbar()
                     } header: {
                         Text(L10n.Tasks.taskDetails)
                     } footer: {
@@ -232,6 +233,7 @@ struct TaskFormView: View {
                             TextField(L10n.Tasks.customInterval, text: $intervalDays)
                                 .keyboardType(.numberPad)
                                 .focused($focusedField, equals: .intervalDays)
+                                .keyboardDismissToolbar()
                         }
 
                         DatePicker(L10n.Tasks.dueDate, selection: $dueDate, displayedComponents: .date)
@@ -274,6 +276,7 @@ struct TaskFormView: View {
                             .focused($focusedField, equals: .estimatedCost)
                     }
                     .listRowBackground(Color.appBackgroundSecondary)
+                    .keyboardDismissToolbar()
 
                     if let errorMessage = viewModel.errorMessage {
                         Section {