backend: add force rescan parameter to scanner

- Add Force bool field to ScanLibraryRequest in handlers
- Pass force param through job params to worker
- Add forceRescan field and SetForce method to MediaScanner
- Modify processMediaFile to delete and re-create existing items when force=true
- Default behavior unchanged (force=false maintains skip-if-exists)

internal/services/media_scanner.go

@@ -76,6 +76,7 @@ type MediaScanner struct {
 	adminID          pgtype.UUID
 	defaultLibraryID pgtype.UUID
 	libraryTypes     map[string][]string
+	forceRescan      bool
 
 	totalFiles int
 	newItems   int
@@ -104,6 +105,10 @@ func (s *MediaScanner) SetAdminID(adminID pgtype.UUID) {
 	s.adminID = adminID
 }
 
+func (s *MediaScanner) SetForce(force bool) {
+	s.forceRescan = force
+}
+
 func (s *MediaScanner) GetStats() (int, int, int) {
 	return s.totalFiles, s.newItems, s.errors
 }
@@ -356,14 +361,25 @@ func (s *MediaScanner) processMediaFile(ctx context.Context, path string) (bool,
 	existingItem, err := s.getMediaItemByFilePath(ctx, path)
 	if err == nil {
 		fmt.Printf("Media item already exists in database: %s (size: %d vs %d)\n", path, existingItem.FileSize.Int64, info.Size())
-		// Media item exists, check if file has changed (by size)
-		if existingItem.FileSize.Int64 != info.Size() {
-			fmt.Printf("File size changed, updating media item: %s\n", path)
-			_ = s.updateMediaItem(ctx, existingItem.ID, path, info)
+
+		// If force rescan is enabled, always re-process
+		if s.forceRescan {
+			fmt.Printf("Force rescan enabled, re-processing existing media item: %s\n", path)
+			// Force update: delete existing and re-create
+			if err := s.db.DeleteMediaItem(ctx, existingItem.ID); err != nil {
+				fmt.Printf("Warning: failed to delete existing media item: %v\n", err)
+			}
+			// Continue to create new entry below
+		} else {
+			// Normal behavior: check if file has changed (by size)
+			if existingItem.FileSize.Int64 != info.Size() {
+				fmt.Printf("File size changed, updating media item: %s\n", path)
+				_ = s.updateMediaItem(ctx, existingItem.ID, path, info)
+				return false, nil
+			}
+			fmt.Printf("Media item already exists with same size, skipping: %s\n", path)
 			return false, nil
 		}
-		fmt.Printf("Media item already exists with same size, skipping: %s\n", path)
-		return false, nil
 	} else if err != pgx.ErrNoRows {
 		fmt.Printf("Database error checking media item existence: %v\n", err)
 		return false, fmt.Errorf("failed to check if media item exists: %v", err)