test(worker): fix set folders job test to properly register folder

The TestWorker_SetFoldersJob test was submitting a set folders job without
first registering the folder with the library through the HTTP API. This caused
the job to fail because the folder wasn't properly tracked.

Changes:
- Call addFolderToLibrary before submitting the set folders job
- Ensures the temporary test directory is properly registered with the library
- Aligns test behavior with actual API workflow where folders must be added first

cmd/server/tests/worker_test.go

@@ -153,6 +153,9 @@ func TestWorker_SetFoldersJob(t *testing.T) {
 	// Create temporary directory
 	tmpDir := t.TempDir()
 
+	// Add folder to library via HTTP API
+	addFolderToLibrary(t, setup, libraryID, tmpDir)
+
 	// Submit set folders job through WorkerInstance
 	job := &services.Job{
 		ID:   uuid.New().String(),