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/repositories/document_repo.go

@@ -8,6 +8,18 @@ import (
 	"github.com/treytartt/casera-api/internal/models"
 )
 
+// DocumentFilter contains optional filter parameters for listing documents.
+type DocumentFilter struct {
+	ResidenceID  *uint
+	DocumentType string
+	Category     string
+	ContractorID *uint
+	IsActive     *bool
+	ExpiringSoon *int
+	Tags         string
+	Search       string
+}
+
 // DocumentRepository handles database operations for documents
 type DocumentRepository struct {
 	db *gorm.DB
@@ -55,6 +67,45 @@ func (r *DocumentRepository) FindByUser(residenceIDs []uint) ([]models.Document,
 	return documents, err
 }
 
+// FindByUserFiltered finds documents accessible to a user with optional filters.
+func (r *DocumentRepository) FindByUserFiltered(residenceIDs []uint, filter *DocumentFilter) ([]models.Document, error) {
+	query := r.db.Preload("CreatedBy").
+		Preload("Residence").
+		Preload("Images").
+		Where("residence_id IN ? AND is_active = ?", residenceIDs, true)
+
+	if filter != nil {
+		if filter.DocumentType != "" {
+			query = query.Where("document_type = ?", filter.DocumentType)
+		}
+		if filter.Category != "" {
+			query = query.Where("category = ?", filter.Category)
+		}
+		if filter.ContractorID != nil {
+			query = query.Where("contractor_id = ?", *filter.ContractorID)
+		}
+		if filter.IsActive != nil {
+			query = query.Where("is_active = ?", *filter.IsActive)
+		}
+		if filter.ExpiringSoon != nil {
+			now := time.Now().UTC()
+			threshold := now.AddDate(0, 0, *filter.ExpiringSoon)
+			query = query.Where("expiry_date IS NOT NULL AND expiry_date > ? AND expiry_date <= ?", now, threshold)
+		}
+		if filter.Tags != "" {
+			query = query.Where("tags LIKE ?", "%"+filter.Tags+"%")
+		}
+		if filter.Search != "" {
+			searchPattern := "%" + filter.Search + "%"
+			query = query.Where("(title ILIKE ? OR description ILIKE ?)", searchPattern, searchPattern)
+		}
+	}
+
+	var documents []models.Document
+	err := query.Order("created_at DESC").Find(&documents).Error
+	return documents, err
+}
+
 // FindWarranties finds all warranty documents
 func (r *DocumentRepository) FindWarranties(residenceIDs []uint) ([]models.Document, error) {
 	var documents []models.Document