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/router/sync.go

@@ -13,7 +13,7 @@ func registerSyncRoutes(cfg *Config) {
 	protected := e.Group("/api", jwtMiddleware)
 
 	// Create handler for sync-specific routes
-	h := handlers.NewHandler(cfg.Queries, cfg.ConnManager, cfg.QueueProcessor)
+	h := handlers.NewHandler(cfg.Queries, cfg.ConnManager, cfg.QueueProcessor, cfg.Cfg)
 
 	// Book matching and unlinked book resolution routes
 	sync := protected.Group("/sync")