feat(server): hot-reload config store and reloadable infra clients

- Replace single Load() with a watching Store that re-reads config files
  (and config.local.yaml) and fans out a ReloadEvent with a per-field diff
  so consumers can decide whether the change is hot-applicable or requires
  a process restart.
- Wrap llm, retrieval, vector store, and object storage clients in
  Reloadable* shells so the bootstrap can swap their underlying impls when
  config changes without re-instantiating handlers.
- Make jwt.Manager and ops TokenIssuer mutable under a lock so secrets and
  TTLs can be rotated live; thread default plan code through a setter on
  the ops AdminUserService.
- Wire ConfigStore through bootstrap and every cmd/main.go, scheduler /
  worker / tenant-api / ops-api start the watcher; services and handlers
  take a config.Provider so they always read current values for things
  like generation.stream_enabled, scheduler dispatch, retrieval, etc.
- Switch shared/config decoding off viper to a Kratos-derived runtime
  package so env placeholders (\${VAR:default}) resolve consistently and
  the same source machinery powers both the loader and the watcher.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

server/cmd/ops-api/main.go

@@ -30,10 +30,12 @@ func main() {
 		configPath = p
 	}
 
-	cfg, err := opsconfig.Load(configPath)
+	configStore, err := opsconfig.NewStore(configPath)
 	if err != nil {
 		log.Fatalf("ops-api load config: %v", err)
 	}
+	defer configStore.Close()
+	cfg := configStore.Current()
 
 	logger, err := observability.NewLogger(cfg.Log.Level, cfg.Log.Format)
 	if err != nil {
@@ -92,6 +94,23 @@ func main() {
 		logger.Sugar().Fatalf("ops-api seed default admin: %v", err)
 	}
 
+	watcherCtx, watcherCancel := context.WithCancel(context.Background())
+	defer watcherCancel()
+	go func() {
+		if err := configStore.Watch(watcherCtx, logger, func(event opsconfig.ReloadEvent) {
+			if event.Current == nil {
+				return
+			}
+			issuer.Update(event.Current.JWT.Secret, event.Current.JWT.AccessTTL)
+			adminUserSvc.UpdateDefaultPlanCode(event.Current.AdminUsers.DefaultPlanCode)
+			if opsconfig.RestartRequired(event.Changes) {
+				logger.Warn("ops config hot reload changed fields that require process restart")
+			}
+		}); err != nil {
+			logger.Warn("ops config hot reload watcher stopped", zap.Error(err))
+		}
+	}()
+
 	if cfg.Server.Mode == "release" {
 		gin.SetMode(gin.ReleaseMode)
 	}
@@ -130,6 +149,7 @@ func main() {
 	<-quit
 
 	logger.Info("ops-api shutting down...")
+	watcherCancel()
 	shutdownCtx, cancel := context.WithTimeout(context.Background(), 10*time.Second)
 	defer cancel()
 	if err := srv.Shutdown(shutdownCtx); err != nil {