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/document_service.go

@@ -56,8 +56,8 @@ func (s *DocumentService) GetDocument(documentID, userID uint) (*responses.Docum
 	return &resp, nil
 }
 
-// ListDocuments lists all documents accessible to a user
-func (s *DocumentService) ListDocuments(userID uint) ([]responses.DocumentResponse, error) {
+// ListDocuments lists all documents accessible to a user, with optional filters.
+func (s *DocumentService) ListDocuments(userID uint, filter *repositories.DocumentFilter) ([]responses.DocumentResponse, error) {
 	// Get residence IDs (lightweight - no preloads)
 	residenceIDs, err := s.residenceRepo.FindResidenceIDsByUser(userID)
 	if err != nil {
@@ -68,7 +68,22 @@ func (s *DocumentService) ListDocuments(userID uint) ([]responses.DocumentRespon
 		return []responses.DocumentResponse{}, nil
 	}
 
-	documents, err := s.documentRepo.FindByUser(residenceIDs)
+	// If a specific residence filter is set, narrow to that single residence (if user has access)
+	if filter != nil && filter.ResidenceID != nil {
+		found := false
+		for _, rid := range residenceIDs {
+			if rid == *filter.ResidenceID {
+				found = true
+				break
+			}
+		}
+		if !found {
+			return nil, apperrors.Forbidden("error.residence_access_denied")
+		}
+		residenceIDs = []uint{*filter.ResidenceID}
+	}
+
+	documents, err := s.documentRepo.FindByUserFiltered(residenceIDs, filter)
 	if err != nil {
 		return nil, apperrors.Internal(err)
 	}