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/observability/monitoring/test_support.rs

@@ -222,6 +222,7 @@ pub(super) fn sample_monitoring_export_api_key(
         None,
         false,
         0,
+        0,
         0.0,
         false,
     )

apps/aether-gateway/src/handlers/admin/observability/usage/analytics_routes/heatmap.rs

@@ -1,10 +1,13 @@
 use crate::handlers::admin::request::AdminAppState;
+use crate::query::usage_heatmap::{
+    list_usage_heatmap_aggregate_rows, read_stats_daily_cutoff_date,
+};
 use crate::GatewayError;
 use aether_admin::observability::stats::round_to;
 use aether_admin::observability::usage::{
     admin_usage_data_unavailable_response, ADMIN_USAGE_DATA_UNAVAILABLE_DETAIL,
 };
-use aether_data_contracts::repository::usage::UsageDailyHeatmapQuery;
+use aether_data_contracts::repository::usage::{StoredUsageDailySummary, UsageDailyHeatmapQuery};
 use axum::{
     body::Body,
     response::{IntoResponse, Response},
@@ -34,17 +37,13 @@ pub(super) async fn build_admin_usage_heatmap_response(
     )
     .unwrap_or_default();
 
-    let summaries = state
-        .summarize_usage_daily_heatmap(&UsageDailyHeatmapQuery {
-            created_from_unix_secs,
-            user_id: None,
-            admin_mode: true,
-        })
-        .await?;
+    let summaries =
+        build_admin_heatmap_summaries(state, created_from_unix_secs, start_date, today).await?;
 
     let grouped: BTreeMap<String, _> = summaries.into_iter().map(|s| (s.date.clone(), s)).collect();
 
     let mut max_requests = 0_u64;
+    let mut active_days = 0_u64;
     let mut cursor = start_date;
     let mut days = Vec::new();
     while cursor <= today {
@@ -61,6 +60,9 @@ pub(super) async fn build_admin_usage_heatmap_response(
                 (0, 0, 0.0, 0.0)
             };
         max_requests = max_requests.max(requests);
+        if requests > 0 {
+            active_days = active_days.saturating_add(1);
+        }
         days.push(json!({
             "date": date_str,
             "requests": requests,
@@ -77,8 +79,59 @@ pub(super) async fn build_admin_usage_heatmap_response(
         "start_date": start_date.to_string(),
         "end_date": today.to_string(),
         "total_days": days.len(),
+        "active_days": active_days,
         "max_requests": max_requests,
         "days": days,
     }))
     .into_response())
 }
+
+async fn build_admin_heatmap_summaries(
+    state: &AdminAppState<'_>,
+    created_from_unix_secs: u64,
+    start_date: chrono::NaiveDate,
+    today: chrono::NaiveDate,
+) -> Result<Vec<StoredUsageDailySummary>, GatewayError> {
+    let query = UsageDailyHeatmapQuery {
+        created_from_unix_secs,
+        user_id: None,
+        admin_mode: true,
+    };
+    let Some(pool) = state.app().postgres_pool() else {
+        return state.summarize_usage_daily_heatmap(&query).await;
+    };
+
+    let Some(cutoff_date) = read_stats_daily_cutoff_date(&pool).await? else {
+        return state.summarize_usage_daily_heatmap(&query).await;
+    };
+
+    let cutoff_day = cutoff_date.date_naive().min(today);
+    let mut summaries =
+        list_usage_heatmap_aggregate_rows(&pool, start_date, cutoff_day, None).await?;
+    let raw_start_date = start_date.max(cutoff_day);
+    if raw_start_date <= today {
+        let raw_start_of_day = raw_start_date
+            .and_hms_opt(0, 0, 0)
+            .expect("heatmap day start should be valid");
+        let raw_created_from_unix_secs = u64::try_from(
+            chrono::DateTime::<chrono::Utc>::from_naive_utc_and_offset(
+                raw_start_of_day,
+                chrono::Utc,
+            )
+            .timestamp(),
+        )
+        .unwrap_or_default();
+        summaries.extend(
+            state
+                .summarize_usage_daily_heatmap(&UsageDailyHeatmapQuery {
+                    created_from_unix_secs: raw_created_from_unix_secs,
+                    user_id: None,
+                    admin_mode: true,
+                })
+                .await?,
+        );
+    }
+
+    summaries.sort_by(|left, right| left.date.cmp(&right.date));
+    Ok(summaries)
+}