feat(model,service): add folder_path and user_id to FileResponse, add user_id filter to ListFiles

- FileResponse gains folder_path ("/" for root) and user_id fields

- folder_id no longer uses omitempty, root files return null

- ListFiles accepts optional userID parameter for filtering by owner

- New buildFileResponse helper populates folder_path from FolderStore

- New GetFileResponse method wraps GetFileMetadata + buildFileResponse

Ultraworked with [Sisyphus](https://github.com/code-yeongyu/oh-my-openagent)

Co-authored-by: Sisyphus <clio-agent@sisyphuslabs.ai>

internal/service/file_service.go

@@ -16,28 +16,59 @@ import (
 
 // FileService handles file listing, metadata, download, and deletion operations.
 type FileService struct {
-	storage   storage.ObjectStorage
-	blobStore *store.BlobStore
-	fileStore *store.FileStore
-	bucket    string
-	db        *gorm.DB
-	logger    *zap.Logger
+	storage     storage.ObjectStorage
+	blobStore   *store.BlobStore
+	fileStore   *store.FileStore
+	folderStore *store.FolderStore
+	bucket      string
+	db          *gorm.DB
+	logger      *zap.Logger
 }
 
 // NewFileService creates a new FileService.
-func NewFileService(storage storage.ObjectStorage, blobStore *store.BlobStore, fileStore *store.FileStore, bucket string, db *gorm.DB, logger *zap.Logger) *FileService {
+func NewFileService(storage storage.ObjectStorage, blobStore *store.BlobStore, fileStore *store.FileStore, folderStore *store.FolderStore, bucket string, db *gorm.DB, logger *zap.Logger) *FileService {
 	return &FileService{
-		storage:   storage,
-		blobStore: blobStore,
-		fileStore: fileStore,
-		bucket:    bucket,
-		db:        db,
-		logger:    logger,
+		storage:     storage,
+		blobStore:   blobStore,
+		fileStore:   fileStore,
+		folderStore: folderStore,
+		bucket:      bucket,
+		db:          db,
+		logger:      logger,
 	}
 }
 
-// ListFiles returns a paginated list of files, optionally filtered by folder or search query.
-func (s *FileService) ListFiles(ctx context.Context, folderID *int64, page, pageSize int, search string) ([]model.FileResponse, int64, error) {
+// buildFileResponse creates a FileResponse from a File and FileBlob, including folder_path and user_id.
+func (s *FileService) buildFileResponse(ctx context.Context, f model.File, blob model.FileBlob) model.FileResponse {
+	resp := model.FileResponse{
+		ID:        f.ID,
+		Name:      f.Name,
+		FolderID:  f.FolderID,
+		UserID:    f.UserID,
+		Size:      blob.FileSize,
+		MimeType:  blob.MimeType,
+		SHA256:    f.BlobSHA256,
+		CreatedAt: f.CreatedAt,
+		UpdatedAt: f.UpdatedAt,
+	}
+
+	// Determine folder_path
+	if f.FolderID != nil && s.folderStore != nil {
+		folder, err := s.folderStore.GetByID(ctx, *f.FolderID)
+		if err == nil && folder != nil {
+			resp.FolderPath = &folder.Path
+		}
+	}
+	if resp.FolderPath == nil {
+		rootPath := "/"
+		resp.FolderPath = &rootPath
+	}
+
+	return resp
+}
+
+// ListFiles returns a paginated list of files, optionally filtered by folder, user, or search query.
+func (s *FileService) ListFiles(ctx context.Context, folderID *int64, userID *int64, page, pageSize int, search string) ([]model.FileResponse, int64, error) {
 	var files []model.File
 	var total int64
 	var err error
@@ -51,6 +82,17 @@ func (s *FileService) ListFiles(ctx context.Context, folderID *int64, page, page
 		return nil, 0, fmt.Errorf("list files: %w", err)
 	}
 
+	// Apply user_id filtering in service layer
+	if userID != nil {
+		filtered := make([]model.File, 0, len(files))
+		for _, f := range files {
+			if f.UserID != nil && *f.UserID == *userID {
+				filtered = append(filtered, f)
+			}
+		}
+		files = filtered
+	}
+
 	responses := make([]model.FileResponse, 0, len(files))
 	for _, f := range files {
 		blob, err := s.blobStore.GetBySHA256(ctx, f.BlobSHA256)
@@ -61,16 +103,7 @@ func (s *FileService) ListFiles(ctx context.Context, folderID *int64, page, page
 			return nil, 0, fmt.Errorf("blob not found for file %d", f.ID)
 		}
 
-		responses = append(responses, model.FileResponse{
-			ID:        f.ID,
-			Name:      f.Name,
-			FolderID:  f.FolderID,
-			Size:      blob.FileSize,
-			MimeType:  blob.MimeType,
-			SHA256:    f.BlobSHA256,
-			CreatedAt: f.CreatedAt,
-			UpdatedAt: f.UpdatedAt,
-		})
+		responses = append(responses, s.buildFileResponse(ctx, f, *blob))
 	}
 
 	return responses, total, nil
@@ -97,6 +130,16 @@ func (s *FileService) GetFileMetadata(ctx context.Context, fileID int64) (*model
 	return file, blob, nil
 }
 
+// GetFileResponse returns a fully populated FileResponse for a given file ID.
+func (s *FileService) GetFileResponse(ctx context.Context, fileID int64) (*model.FileResponse, error) {
+	file, blob, err := s.GetFileMetadata(ctx, fileID)
+	if err != nil {
+		return nil, err
+	}
+	resp := s.buildFileResponse(ctx, *file, *blob)
+	return &resp, nil
+}
+
 // DownloadFile returns a reader for the file content, along with file and blob metadata.
 // If rangeHeader is non-empty, it parses the range and returns partial content.
 func (s *FileService) DownloadFile(ctx context.Context, fileID int64, rangeHeader string) (io.ReadCloser, *model.File, *model.FileBlob, int64, int64, error) {