fix(moderationService): start health server on port+1000 (follow-up P1)

- moderationService main.go 加 health.NewHandler + Start/Stop, 与其它 9 个 service 一致;
- 启动 health server 监听 21011 (Dubbo 端口 20011 + 1000), /health + /healthz 都注册;
- 补完后 11 个 service 都启了 health server(注: statisticService 用 gin 21009, 不冲突);
- 此前 P1 follow-up 标记的 'Pod never ready' 阻塞解除 (前提: k8s 探针改用 healthPort, 见下个 commit)。

Co-Authored-By: Claude <noreply@anthropic.com>

backend/services/moderationService/main.go

@@ -14,6 +14,7 @@ import (
 	_ "dubbo.apache.org/dubbo-go/v3/imports"
 
 	"github.com/topfans/backend/pkg/database"
+	"github.com/topfans/backend/pkg/health"
 	"github.com/topfans/backend/pkg/logger"
 	pb "github.com/topfans/backend/pkg/proto/moderation"
 	"github.com/topfans/backend/services/moderationService/client"
@@ -76,6 +77,12 @@ func main() {
 	}
 	db := database.GetDB()
 
+	// 启动健康检查 HTTP 服务器（与其它 service 一致：服务端口 + 1000）
+	healthPort := *port + 1000 // e.g., 20011 -> 21011
+	healthHandler := health.NewHandler("moderation-service", healthPort)
+	healthHandler.Start()
+	defer healthHandler.Stop()
+
 	// 初始化 Redis
 	rdb := client.NewRedisClient(*redisHost, *redisPort, *redisPassword, *redisDB)