feat(scanner): add debounced file watching with polling fallback

- Implement event queue with 3-second debouncing for file system events
- Add configurable polling fallback (default 3 min) via SCAN_POLL_INTERVAL_MINUTES
- Add SyncFilesystemWithDatabase to detect orphaned DB entries and new files
- Integrate utils.ResolveMediaURL for consistent media file path resolution
- Add COOKIE_SECURE env var with SameSite=LaxMode for session cookies
- Update media handler to properly decode URL paths for file serving
- Refactor scanner initialization to accept poll interval configuration

internal/services/worker.go

@@ -199,7 +199,7 @@ func (w *Worker) processScanJob(job *Job) (interface{}, error) {
 		force = forceVal
 	}
 
-	scanner := NewMediaScanner(db)
+	scanner := NewMediaScanner(db, 0)
 	scanner.job = job
 
 	job.ProgressCallback = func(progress float64, filesScanned, newItems, errors int) {