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/tenant/app/brand_service.go

@@ -6,6 +6,7 @@ import (
 	"errors"
 	"fmt"
 	"strings"
+	"sync"
 	"time"
 
 	"github.com/jackc/pgx/v5"
@@ -24,6 +25,7 @@ import (
 type BrandService struct {
 	pool           *pgxpool.Pool
 	monitoringPool *pgxpool.Pool
+	limitsMu       sync.RWMutex
 	limits         sharedconfig.BrandLibraryConfig
 	auditLogs      *auditlog.AsyncWriter
 	cache          sharedcache.Cache
@@ -39,6 +41,24 @@ func (s *BrandService) WithCache(c sharedcache.Cache) *BrandService {
 	return s
 }
 
+func (s *BrandService) UpdateConfig(limits sharedconfig.BrandLibraryConfig) {
+	if s == nil {
+		return
+	}
+	s.limitsMu.Lock()
+	s.limits = limits
+	s.limitsMu.Unlock()
+}
+
+func (s *BrandService) currentLimits() sharedconfig.BrandLibraryConfig {
+	if s == nil {
+		return sharedconfig.BrandLibraryConfig{}
+	}
+	s.limitsMu.RLock()
+	defer s.limitsMu.RUnlock()
+	return s.limits
+}
+
 // --- Brand CRUD ---
 
 type BrandRequest struct {
@@ -809,11 +829,12 @@ func (s *BrandService) loadBrandLibrarySummary(ctx context.Context, tenantID int
 		return nil, err
 	}
 
-	maxBrands := s.limits.BrandLimitForPlan(plan.PlanCode)
+	limits := s.currentLimits()
+	maxBrands := limits.BrandLimitForPlan(plan.PlanCode)
 	if plan.MaxBrands > 0 {
 		maxBrands = plan.MaxBrands
 	}
-	maxKeywords := s.limits.MaxKeywords
+	maxKeywords := limits.MaxKeywords
 
 	return &BrandLibrarySummaryResponse{
 		PlanCode:               plan.PlanCode,
@@ -824,15 +845,16 @@ func (s *BrandService) loadBrandLibrarySummary(ctx context.Context, tenantID int
 		MaxKeywords:            maxKeywords,
 		UsedKeywords:           usage.KeywordCount,
 		RemainingKeywords:      maxInt(maxKeywords-usage.KeywordCount, 0),
-		MaxQuestionsPerKeyword: s.limits.MaxQuestionsPerKeyword,
+		MaxQuestionsPerKeyword: limits.MaxQuestionsPerKeyword,
 	}, nil
 }
 
 func (s *BrandService) loadBrandLibraryPlan(ctx context.Context, tenantID int64) (*brandLibraryPlan, error) {
+	limits := s.currentLimits()
 	plan := &brandLibraryPlan{
 		PlanCode:  "free",
 		PlanName:  "",
-		MaxBrands: s.limits.BrandLimitForPlan("free"),
+		MaxBrands: limits.BrandLimitForPlan("free"),
 	}
 
 	var quotaPolicyJSON []byte