feat(stats): 新增聚合读路径与回填机制并重构 dashboard/usage 读取链路

- 新增 stats_user_summary 及 user_daily_provider/api_format/cost_savings 等聚合表
- 扩展 stats_daily/hourly 有效 token 与响应时间等字段，maintenance runtime 同步写入
- 新增 backfill 模块与 --apply-backfills 命令补齐历史聚合数据
- 重写 dashboard_filters、usage_heatmap、user_rollups 查询改走聚合表
- 同步更新 baseline_v2.sql 与 migration 集，README/dev.sh 补充回填用法

apps/aether-gateway/src/handlers/admin/users/api_keys/responses/create.rs

@@ -142,6 +142,7 @@ pub(crate) async fn build_admin_create_user_api_key_response(
             expires_at_unix_secs: None,
             auto_delete_on_expiry: false,
             total_requests: 0,
+            total_tokens: 0,
             total_cost_usd: 0.0,
         })
         .await?

apps/aether-gateway/src/handlers/admin/users/lifecycle/reads.rs

@@ -4,6 +4,7 @@ use super::support::{
 };
 use crate::handlers::admin::request::{AdminAppState, AdminRequestContext};
 use crate::handlers::admin::shared::{query_param_optional_bool, query_param_value};
+use crate::query::user_rollups::list_user_usage_totals_from_stats_summary;
 use crate::GatewayError;
 use axum::{
     body::Body,
@@ -42,10 +43,19 @@ pub(in super::super) async fn build_admin_list_users_response(
         .iter()
         .map(|row| row.id.clone())
         .collect::<Vec<_>>();
+    let usage_totals_future = async {
+        let Some(pool) = state.app().postgres_pool() else {
+            return state.summarize_usage_totals_by_user_ids(&user_ids).await;
+        };
+        match list_user_usage_totals_from_stats_summary(&pool, &user_ids).await? {
+            Some(items) => Ok(items),
+            None => state.summarize_usage_totals_by_user_ids(&user_ids).await,
+        }
+    };
     let (auth_rows_result, wallet_rows_result, usage_totals_result) = tokio::join!(
         state.list_user_auth_by_ids(&user_ids),
         state.list_wallet_snapshots_by_user_ids(&user_ids),
-        state.summarize_usage_totals_by_user_ids(&user_ids),
+        usage_totals_future,
     );
     let auth_by_user_id = auth_rows_result?
         .into_iter()