refactor: inject ConnectionManager into Worker

Pass ConnectionManager to Worker constructor to enable WebSocket
broadcasting capabilities. Updated:
- main.go: server initialization
- test_helpers.go: test setup
- commonhandlers.go: handler initialization

This change enables Worker to broadcast job updates to connected clients.

cmd/server/main.go

@@ -105,7 +105,7 @@ func main() {
 	libraryService := services.NewLibraryService(queries)
 
 	// Create worker for background tasks
-	worker := services.NewWorker(3)
+	worker := services.NewWorker(3, connManager)
 	services.WorkerInstance = worker
 
 	koreaderHandler := handlers.NewKOReaderHandler(queries, connManager, queueProcessor)