新功能(#77): 套餐列表返回促销信息

- 新增 SubscribePromo 响应结构，套餐列表每项追加 promo 字段
- 新增 promo.go 促销候选规则查询与资格评估逻辑
- 重构 authMiddleware 提取 authenticateRequest，新增 OptionalAuthMiddleware
- /v1/public/subscribe/list 改为可选鉴权，未登录仅展示 campaign 类型促销
- /node/list、/group/list 保持强制鉴权不变
- 每个规格只返回最高优先级命中的规则，promo_price 为单价，expires_at 为秒级时间戳
- 新增单测覆盖 campaign/new_user 命中、活动窗口判定等场景

Co-authored-by: multica-agent <github@multica.ai>

internal/handler/routes.go

@@ -978,17 +978,16 @@ func RegisterHandlers(router *gin.Engine, serverCtx *svc.ServiceContext) {
 	}
 
 	publicSubscribeGroupRouter := router.Group("/v1/public/subscribe")
-	publicSubscribeGroupRouter.Use(middleware.AuthMiddleware(serverCtx), middleware.DeviceMiddleware(serverCtx))
 
 	{
 		// Get subscribe list
-		publicSubscribeGroupRouter.GET("/list", publicSubscribe.QuerySubscribeListHandler(serverCtx))
+		publicSubscribeGroupRouter.GET("/list", middleware.OptionalAuthMiddleware(serverCtx), middleware.DeviceMiddleware(serverCtx), publicSubscribe.QuerySubscribeListHandler(serverCtx))
 
 		// Get user subscribe node info
-		publicSubscribeGroupRouter.GET("/node/list", publicSubscribe.QueryUserSubscribeNodeListHandler(serverCtx))
+		publicSubscribeGroupRouter.GET("/node/list", middleware.AuthMiddleware(serverCtx), middleware.DeviceMiddleware(serverCtx), publicSubscribe.QueryUserSubscribeNodeListHandler(serverCtx))
 
 		// Get subscribe group list
-		publicSubscribeGroupRouter.GET("/group/list", publicSubscribe.QuerySubscribeGroupListHandler(serverCtx))
+		publicSubscribeGroupRouter.GET("/group/list", middleware.AuthMiddleware(serverCtx), middleware.DeviceMiddleware(serverCtx), publicSubscribe.QuerySubscribeGroupListHandler(serverCtx))
 	}
 
 	publicTicketGroupRouter := router.Group("/v1/public/ticket")