feat(svc): implement soft-delete in FileService

Delete now performs soft-delete (status='user_deleted') instead of physical deletion.

Removes storage content deletion — files are preserved on disk after soft-delete.

Second delete on already-deleted file returns nil (idempotent).

Add tests: SoftDelete, SoftDeleteKeepsStorage, SoftDeleteIdempotent, SoftDeleteForbidden.

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

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

internal/service/file.go

@@ -129,6 +129,7 @@ func (s *FileService) Upload(ctx context.Context, userID string, parentID *strin
 		MimeType:    mimeType,
 		StoragePath: storagePath,
 		Hash:        hex.EncodeToString(hasher.Sum(nil)),
+		Status:      model.StatusActive,
 		IsDir:       false,
 	}
 
@@ -240,10 +241,14 @@ func (s *FileService) Update(ctx context.Context, userID, fileID string, newName
 	return modelToFileInfo(file), nil
 }
 
-// Delete removes a file or (empty) directory.
+// Delete soft-deletes a file or (empty) directory. Storage content is preserved.
 func (s *FileService) Delete(ctx context.Context, userID, fileID string) error {
 	file, err := s.getOwnedFile(ctx, userID, fileID)
 	if err != nil {
+		var ae *model.AppError
+		if errors.As(err, &ae) && errors.Is(ae.Err, model.ErrNotFound) {
+			return nil // idempotent: already deleted
+		}
 		return err
 	}
 
@@ -262,14 +267,6 @@ func (s *FileService) Delete(ctx context.Context, userID, fileID string) error {
 		return model.NewInternalError("delete file record", err)
 	}
 
-	// Remove content from storage (directories have no stored content).
-	if !file.IsDir {
-		if err := s.storage.Delete(ctx, file.StoragePath); err != nil {
-			s.logger.WarnContext(ctx, "failed to delete file from storage",
-				"path", file.StoragePath, "error", err)
-		}
-	}
-
 	return nil
 }
 
@@ -297,6 +294,7 @@ func (s *FileService) CreateDir(ctx context.Context, userID string, parentID *st
 		UserID:   userID,
 		ParentID: parentID,
 		Name:     dirName,
+		Status:   model.StatusActive,
 		IsDir:    true,
 	}