feat: add hook system, QR code login, and layered cache

- Implement extensible hook system for content moderation with
  builtin and AI-powered moderation hooks
- Add QR code login feature with SSE for real-time status updates
  and scan/confirm/cancel workflow
- Introduce layered cache with local LRU + Redis backend for
  improved read performance
- Refactor post and comment services to use hook-based moderation
  instead of direct AI service calls
- Add local cache configuration options (size, buckets, ttl)

cmd/server/wire.go

@@ -45,6 +45,7 @@ func ProvideRouter(
 	adminGroupHandler *handler.AdminGroupHandler,
 	adminDashboardHandler *handler.AdminDashboardHandler,
 	adminLogHandler *handler.AdminLogHandler,
+	qrcodeHandler *handler.QRCodeHandler,
 	logService *service.LogService,
 	activityService service.UserActivityService,
 	casbinService service.CasbinService,
@@ -71,6 +72,7 @@ func ProvideRouter(
 		adminGroupHandler,
 		adminDashboardHandler,
 		adminLogHandler,
+		qrcodeHandler,
 		logService,
 		activityService,
 		casbinService,