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.go

@@ -103,7 +103,11 @@ func (s *TaskService) GetTask(taskID, userID uint) (*responses.TaskResponse, err
 
 // ListTasks lists all tasks accessible to a user as a kanban board.
 // The `now` parameter should be the start of day in the user's timezone for accurate overdue detection.
-func (s *TaskService) ListTasks(userID uint, now time.Time) (*responses.KanbanBoardResponse, error) {
+func (s *TaskService) ListTasks(userID uint, daysThreshold int, now time.Time) (*responses.KanbanBoardResponse, error) {
+	if daysThreshold <= 0 {
+		daysThreshold = 30 // Default
+	}
+
 	// Get all residence IDs accessible to user (lightweight - no preloads)
 	residenceIDs, err := s.residenceRepo.FindResidenceIDsByUser(userID)
 	if err != nil {
@@ -114,13 +118,13 @@ func (s *TaskService) ListTasks(userID uint, now time.Time) (*responses.KanbanBo
 		// Return empty kanban board
 		return &responses.KanbanBoardResponse{
 			Columns:       []responses.KanbanColumnResponse{},
-			DaysThreshold: 30,
+			DaysThreshold: daysThreshold,
 			ResidenceID:   "all",
 		}, nil
 	}
 
 	// Get kanban data aggregated across all residences using user's timezone-aware time
-	board, err := s.taskRepo.GetKanbanDataForMultipleResidences(residenceIDs, 30, now)
+	board, err := s.taskRepo.GetKanbanDataForMultipleResidences(residenceIDs, daysThreshold, now)
 	if err != nil {
 		return nil, apperrors.Internal(err)
 	}