refactor: expose electric data freshness

src/server/routes/energy/index.ts

@@ -527,7 +527,8 @@ app.get('/electric/overview', async (c) => {
        SUM(CASE WHEN DATE_FORMAT(start_time, '%Y-%m') = DATE_FORMAT(CURDATE(), '%Y-%m')
                 THEN fee ELSE 0 END) AS monthFee,
        SUM(CASE WHEN DATE(start_time) = CURDATE() THEN kwh ELSE 0 END) AS todayKwh,
-       SUM(CASE WHEN DATE(start_time) = CURDATE() THEN fee ELSE 0 END) AS todayFee
+       SUM(CASE WHEN DATE(start_time) = CURDATE() THEN fee ELSE 0 END) AS todayFee,
+       DATE_FORMAT(MAX(start_time), '%Y-%m-%d %H:%i:%s') AS latestRecordAt
      FROM bi_ele_charge_record`,
   );
   const k = kpiRows[0] ?? {};
@@ -537,6 +538,7 @@ app.get('/electric/overview', async (c) => {
   const monthFee  = Number(k.monthFee)  || 0;
   const todayKwh  = Number(k.todayKwh)  || 0;
   const todayFee  = Number(k.todayFee)  || 0;
+  const latestRecordAt = k.latestRecordAt ? String(k.latestRecordAt) : null;
 
   // 本月每日（用于柱图）
   const [trendRows] = await pool.query<RowDataPacket[]>(
@@ -589,6 +591,7 @@ app.get('/electric/overview', async (c) => {
   return {
     kpi: { totalKwh, totalFee, monthKwh, monthFee, todayKwh, todayFee, todayChainPct },
     trend: trendArr,
+    latestRecordAt,
   };
   }, { force });
   return c.json(data);