refactor(scheduler): migrate outbox and model registry to scheduler-based execution

Replace internal goroutine-based timing loops with scheduler integration
for SyncOutboxService and ModelRegistryService. Both services now expose
RunOnce() methods called by the central scheduler instead of managing
their own background loops.

- Add Interval() and RunOnce() methods to SyncOutboxService
- Add RefreshEvery() and RunOnce() methods to ModelRegistryService
- Remove started flag from SyncOutboxService struct
- Move scheduler.Start() after all services are initialized
- Ensure initial model registry refresh before scheduler starts

internal/service/sync_outbox.go

@@ -36,11 +36,10 @@ type SyncOutboxEntry struct {
 
 // SyncOutboxService retries failed sync operations stored in the database.
 type SyncOutboxService struct {
-	db      *gorm.DB
-	sync    *SyncService
-	cfg     SyncOutboxConfig
-	logger  *slog.Logger
-	started bool
+	db     *gorm.DB
+	sync   *SyncService
+	cfg    SyncOutboxConfig
+	logger *slog.Logger
 }
 
 func NewSyncOutboxService(db *gorm.DB, sync *SyncService, cfg SyncOutboxConfig, logger *slog.Logger) *SyncOutboxService {
@@ -63,6 +62,13 @@ func (s *SyncOutboxService) Enabled() bool {
 	return s != nil && s.cfg.Enabled
 }
 
+func (s *SyncOutboxService) Interval() time.Duration {
+	if s == nil || s.cfg.Interval <= 0 {
+		return 5 * time.Second
+	}
+	return s.cfg.Interval
+}
+
 // Enqueue persists a failed sync operation for retry.
 func (s *SyncOutboxService) Enqueue(entry SyncOutboxEntry) error {
 	if s == nil || !s.cfg.Enabled {
@@ -101,24 +107,12 @@ func (s *SyncOutboxService) Enqueue(entry SyncOutboxEntry) error {
 	return nil
 }
 
-// Start begins the background retry loop.
-func (s *SyncOutboxService) Start(ctx context.Context) {
-	if s == nil || !s.cfg.Enabled || s.started {
+// RunOnce processes one batch of pending outbox items. Called by scheduler.
+func (s *SyncOutboxService) RunOnce(ctx context.Context) {
+	if s == nil || !s.cfg.Enabled {
 		return
 	}
-	s.started = true
-
-	ticker := time.NewTicker(s.cfg.Interval)
-	defer ticker.Stop()
-
-	for {
-		select {
-		case <-ctx.Done():
-			return
-		case <-ticker.C:
-			s.processBatch(ctx)
-		}
-	}
+	s.processBatch(ctx)
 }
 
 func (s *SyncOutboxService) processBatch(ctx context.Context) {