perf(clickhouse): Phase 2 legacy governance — TTL cleanup, unified pool, MV, ops API

- Replace retention ALTER DELETE with MATERIALIZE TTL; use TRUNCATE for delete-all
- Remove GORM ClickHouse pool; migrate user access log reads to ChConn
- Drop query-side trim(remote_addr); enable wait_for_async_insert=1
- Add of_node_traffic_hourly MV and dashboard traffic trend fallback
- Add GET /admin/status/clickhouse operational metrics endpoint

internal/apps/admin/logs/routers.go

@@ -248,7 +248,7 @@ func enrichAccessLogsWithUsers(ctx context.Context, list []accessLogItem) {
 // @Router /api/v1/admin/logs/access [get]
 func GetAccessLogs(c *gin.Context) {
 	ctx := c.Request.Context()
-	if !config.Config.ClickHouse.Enabled || db.ChDB(ctx) == nil {
+	if !config.Config.ClickHouse.Enabled || !db.ChConnReady() {
 		response.AbortWithError(c, http.StatusBadRequest, "ClickHouse 存储服务未启用，无法检索访问日志")
 		return
 	}
@@ -348,7 +348,7 @@ type logsAnalyticsResponse struct {
 // @Router /api/v1/admin/logs/analytics [get]
 func GetLogsAnalytics(c *gin.Context) {
 	ctx := c.Request.Context()
-	if !config.Config.ClickHouse.Enabled || db.ChDB(ctx) == nil {
+	if !config.Config.ClickHouse.Enabled || !db.ChConnReady() {
 		response.AbortWithError(c, http.StatusBadRequest, "ClickHouse 存储服务未启用，无法获取分析数据")
 		return
 	}