Fix backend API parity: document filters, task days param, i18n locales, contract tests

- Add document list filter support (residence, type, category, contractor, is_active, expiring_soon, search) to handler/service/repo
- Add `days` query param parsing to ListTasks handler (matches ListTasksByResidence)
- Add `error.invalid_token` i18n key to all 9 non-English locale files
- Update contract test to include VerificationResponse mapping

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

internal/services/task_service_test.go

@@ -155,7 +155,7 @@ func TestTaskService_ListTasks(t *testing.T) {
 	testutil.CreateTestTask(t, db, residence.ID, user.ID, "Task 2")
 	testutil.CreateTestTask(t, db, residence.ID, user.ID, "Task 3")
 
-	resp, err := service.ListTasks(user.ID, time.Now().UTC())
+	resp, err := service.ListTasks(user.ID, 30, time.Now().UTC())
 	require.NoError(t, err)
 	// ListTasks returns a KanbanBoardResponse with columns
 	// Count total tasks across all columns