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/internal/ops/app/admin_user.go

@@ -6,6 +6,7 @@ import (
 	"net/mail"
 	"regexp"
 	"strings"
+	"sync"
 	"time"
 
 	"github.com/jackc/pgx/v5/pgconn"
@@ -35,6 +36,7 @@ var phonePattern = regexp.MustCompile(`^\+?[0-9]{6,20}$`)
 type AdminUserService struct {
 	users           *repository.AdminUserRepository
 	audits          *AuditService
+	configMu        sync.RWMutex
 	defaultPlanCode string
 }
 
@@ -50,6 +52,31 @@ func NewAdminUserService(users *repository.AdminUserRepository, audits *AuditSer
 	}
 }
 
+func (s *AdminUserService) UpdateDefaultPlanCode(defaultPlanCode string) {
+	if s == nil {
+		return
+	}
+	defaultPlanCode = strings.TrimSpace(defaultPlanCode)
+	if defaultPlanCode == "" {
+		defaultPlanCode = "free"
+	}
+	s.configMu.Lock()
+	s.defaultPlanCode = defaultPlanCode
+	s.configMu.Unlock()
+}
+
+func (s *AdminUserService) currentDefaultPlanCode() string {
+	if s == nil {
+		return "free"
+	}
+	s.configMu.RLock()
+	defer s.configMu.RUnlock()
+	if strings.TrimSpace(s.defaultPlanCode) == "" {
+		return "free"
+	}
+	return s.defaultPlanCode
+}
+
 type AdminUserView struct {
 	ID                 int64      `json:"id"`
 	Email              *string    `json:"email"`
@@ -295,7 +322,7 @@ func (s *AdminUserService) Create(ctx context.Context, actor *Actor, in CreateAd
 	}
 	planCode := strings.TrimSpace(in.PlanCode)
 	if planCode == "" {
-		planCode = s.defaultPlanCode
+		planCode = s.currentDefaultPlanCode()
 	}
 	role := strings.TrimSpace(in.Role)
 	if role == "" {