feat(worker): broadcast scan_complete WebSocket message on scan job finish

The MessageTypeScanComplete constant existed but was never actually sent by
the worker. This meant the frontend had no way to know when a scan finished.

- After a JobTypeScan completes, broadcast scan_complete to the job's user
  via WebSocket ConnectionManager
- Includes job_id, files_scanned, new_items, and errors in the payload
- Only broadcasts for JobTypeScan (not other job types) when connManager
  is available and job.UserID is set

internal/services/worker.go

@@ -305,6 +305,19 @@ func (w *Worker) processJob(job *Job) {
 		NewItems:     newItems,
 		Errors:       errors,
 	}
+
+	if job.Type == JobTypeScan && w.connManager != nil && job.UserID != "" {
+		w.connManager.BroadcastToUser(job.UserID, wsync.BroadcastMessage{
+			Type: wsync.MessageTypeScanComplete,
+			Data: map[string]interface{}{
+				"job_id":        job.ID,
+				"files_scanned": filesScanned,
+				"new_items":     newItems,
+				"errors":        errors,
+			},
+		})
+	}
+
 	w.mu.Unlock()
 }
 
@@ -888,9 +901,9 @@ func (w *Worker) processDirectoryScanJob(job *Job) (interface{}, error) {
 	// Create temporary scanner instance for this job
 	scanner := NewMediaScanner(db)
 	scanner.job = job
-	// Find which library owns this directory
+	// Find which library owns this directory (prefix match for subdirectories)
 	ctx := context.Background()
-	libRow, err := db.GetLibraryByFolder(ctx, directory)
+	libRow, err := db.GetLibraryByFolderPathPrefix(ctx, directory)
 	if err != nil {
 		return nil, fmt.Errorf("directory not associated with any library: %s", directory)
 	}