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/model_registry.go

@@ -81,26 +81,23 @@ func NewModelRegistryService(db *gorm.DB, rdb *redis.Client, cfg ModelRegistryCo
 	}
 }
 
-func (s *ModelRegistryService) Start(ctx context.Context) {
+func (s *ModelRegistryService) Enabled() bool {
+	return s != nil && s.cfg.Enabled
+}
+
+func (s *ModelRegistryService) RefreshEvery() time.Duration {
+	if s == nil || s.cfg.RefreshEvery <= 0 {
+		return 30 * time.Minute
+	}
+	return s.cfg.RefreshEvery
+}
+
+// RunOnce triggers a single model registry refresh. Called by scheduler.
+func (s *ModelRegistryService) RunOnce(ctx context.Context) {
 	if !s.cfg.Enabled {
 		return
 	}
-	go func() {
-		ticker := time.NewTicker(s.cfg.RefreshEvery)
-		defer ticker.Stop()
-
-		// Best-effort initial refresh.
-		_ = s.Refresh(ctx, "")
-
-		for {
-			select {
-			case <-ctx.Done():
-				return
-			case <-ticker.C:
-				_ = s.Refresh(ctx, "")
-			}
-		}
-	}()
+	_ = s.Refresh(ctx, "")
 }
 
 type ModelRegistryStatus struct {