feat(backup): tap automatic-backups to make a copy now

apps/app_seeds/test/services/auto_backup_service_test.dart

@@ -139,6 +139,21 @@ void main() {
     ]);
   });
 
+  test('backupNow writes even when a copy is not yet due', () async {
+    final store = AutoBackupStore(InMemorySecretStore());
+    await store.markBackupAt(DateTime.utc(2026, 7, 10)); // today: not due
+    final service = newService(
+      newExporter(),
+      store: store,
+      now: DateTime.utc(2026, 7, 10),
+    );
+
+    // runIfDue is a no-op today, but an explicit tap still makes a copy.
+    expect(await service.runIfDue(), isFalse);
+    expect(await service.backupNow(), isTrue);
+    expect(autoCopies(), ['tanemaki-auto-2026-07-10.tanemaki']);
+  });
+
   test('a failed backup returns false and never throws', () async {
     final service = newService(
       _ThrowingExporter(db),

apps/app_seeds/test/ui/backup_section_test.dart

@@ -9,6 +9,8 @@ import 'package:tane/data/export_import/inventory_json_codec.dart';
 import 'package:tane/db/database.dart';
 import 'package:tane/i18n/strings.g.dart';
 import 'package:tane/security/secure_key_store.dart';
+import 'package:tane/services/auto_backup_service.dart';
+import 'package:tane/services/auto_backup_store.dart';
 import 'package:tane/services/export_import_service.dart';
 import 'package:tane/services/file_service.dart';
 import 'package:tane/services/recovery_sheet_service.dart';
@@ -232,4 +234,46 @@ void main() {
     // of the sheet. Just assert it saved and confirmed.
     expect(find.text('Copy saved'), findsOneWidget);
   });
+
+  testWidgets('tapping the automatic-backups line makes a copy now', (
+    tester,
+  ) async {
+    final spy = _SpyAutoBackup(db);
+    await tester.pumpWidget(
+      wrap(
+        Scaffold(
+          body: BackupSection(service: service, sheet: sheet, autoBackup: spy),
+        ),
+      ),
+    );
+    await tester.pump(); // resolve the "last copy" future
+
+    await tester.tap(find.text('Automatic backups'));
+    await tester.pumpAndSettle();
+
+    expect(spy.calls, 1);
+    expect(find.text('Copy saved'), findsOneWidget);
+  });
+}
+
+/// Counts explicit "back up now" taps without touching the disk.
+class _SpyAutoBackup extends AutoBackupService {
+  _SpyAutoBackup(AppDatabase db)
+    : super(
+        exporter: ExportImportService(
+          repository: newTestRepository(db),
+          files: FakeFileService(),
+          keys: SecureKeyStore(store: InMemorySecretStore()),
+        ),
+        store: AutoBackupStore(InMemorySecretStore()),
+        directory: () async => throw UnimplementedError(),
+      );
+
+  int calls = 0;
+
+  @override
+  Future<bool> backupNow() async {
+    calls++;
+    return true;
+  }
 }