feat: 排行榜日快照分析 + 数据库连接池/索引调优

- 排行榜改为按天预计算快照(admin_leaderboard_daily_stats),请求只读取合并,重统计移至后台调度;过去日不可变、当天 TTL 刷新,避免在线聚合长时间占用数据库
- 为 runs/tool_call_metrics/llm_call_metrics/threads_meta 增加面向时间段+用户聚合的复合索引(model __table_args__ + migration 20260608_01)
- 连接池可调:DatabaseConfig 新增 max_overflow / pool_timeout,接入 postgres/mysql 引擎;config.yaml 上调 pool_size=20/max_overflow=20
- 新增手动执行的索引脚本 scripts/sql/leaderboard_indexes_mysql.sql(幂等,适用于已存在数据、create_all 不补索引且 alembic 关闭的部署)

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

frontend-web/src/core/admin/hooks.ts

@@ -9,6 +9,7 @@ import {
   getUserMemory,
   getUserAnalytics,
   getUserLeaderboard,
+  listUserQa,
   listUserThreadMessages,
   listUserThreads,
   replaceAdminMemoryEntry,
@@ -75,6 +76,17 @@ export function useUserThreads(userId: string | null) {
   });
 }
 
+export function useUserQa(
+  userId: string | null,
+  params: { page: number; pageSize: number; q?: string },
+) {
+  return useQuery({
+    queryKey: ["admin-activity", "qa", userId, params.page, params.pageSize, params.q ?? ""],
+    queryFn: () => listUserQa(userId!, params),
+    enabled: !!userId,
+  });
+}
+
 /** Messages of a given thread. Disabled until a thread is picked. */
 export function useUserThreadMessages(
   userId: string | null,