refactor: show mileage data freshness

src/modules/mileage/MonitoringView.tsx

@@ -23,6 +23,7 @@ import {
   parseMileageDrillContext,
   type MileageDrillContext,
 } from './drill-context';
+import { formatMileageSnapshotTime } from './data-freshness';
 
 const HIGH_MILEAGE_ALERT_TARGETS = new Set([
   '交投40辆4.5T普货',
@@ -494,7 +495,7 @@ export default function MonitoringView() {
   const [pageLoading, setPageLoading] = useState(true);
   const [pageError, setPageError] = useState<{ message: string; scope: 'first' | 'more' } | null>(null);
   const [manualRefreshing, setManualRefreshing] = useState(false);
-  const [lastRefreshedAt, setLastRefreshedAt] = useState<Date | null>(null);
+  const [dataUpdatedAt, setDataUpdatedAt] = useState<string | null>(null);
   const [showBackToTop, setShowBackToTop] = useState(false);
   const [relativeNow, setRelativeNow] = useState(() => Date.now());
   const PAGE_SIZE = 50;
@@ -599,7 +600,7 @@ export default function MonitoringView() {
       setTotal(d.total);
       setPage(1);
       setHasMore(d.page < d.totalPages);
-      setLastRefreshedAt(new Date());
+      setDataUpdatedAt(d.updatedAt);
     }).catch(error => {
       setPageError({
         message: error instanceof Error ? error.message : '里程数据加载失败，请稍后重试',
@@ -651,6 +652,7 @@ export default function MonitoringView() {
       setVehicles(prev => [...prev, ...d.vehicles]);
       setPage(nextPage);
       setHasMore(nextPage < d.totalPages);
+      setDataUpdatedAt(d.updatedAt);
     }).catch(error => {
       setPageError({
         message: error instanceof Error ? error.message : '更多车辆加载失败，请稍后重试',
@@ -762,6 +764,7 @@ export default function MonitoringView() {
       setFullscreenVehicles(d.vehicles);
       setFullscreenStats(d.stats);
       setFilterOptions(d.filters);
+      setDataUpdatedAt(d.updatedAt);
     }).catch(() => {}).finally(() => setFullscreenLoading(false));
   }, [isFullscreen, sortBy, sortOrder, searchTerm, filterDept, filterCustomer, filterRentStatus, filterPlatePrefix, filterTargetNames, filterRegion, filterPlates, rangeStart, rangeEnd, fullscreenRefresh, filterBrands, sourcePriority]);
 
@@ -1078,14 +1081,19 @@ export default function MonitoringView() {
               </div>
               <div className="mt-1 flex items-center gap-1.5">
                 <span className="h-1.5 w-1.5 rounded-full bg-blue-500" />
-                <span className="text-[9px] font-bold uppercase tracking-tight text-slate-400">数据监控 • OneOS 实时查询</span>
+                <span
+                  className="truncate text-[9px] font-bold tracking-tight text-slate-400"
+                  title={`OneOS 分钟级快照 · 数据截至 ${formatMileageSnapshotTime(dataUpdatedAt)}`}
+                >
+                  OneOS 分钟级快照 · 截至 {formatMileageSnapshotTime(dataUpdatedAt)}
+                </span>
               </div>
             </div>
           </div>
 
           <div className="flex flex-shrink-0 items-center gap-1.5">
             <span className="hidden text-[9px] font-bold tabular-nums text-slate-400 sm:inline">
-              {lastRefreshedAt ? lastRefreshedAt.toLocaleTimeString('zh-CN', { hour12: false }) : '--:--:--'}
+              数据截至 {formatMileageSnapshotTime(dataUpdatedAt)}
             </span>
             <button
               type="button"

src/modules/mileage/data-freshness.test.ts

@@ -0,0 +1,12 @@
+import assert from 'node:assert/strict';
+import test from 'node:test';
+import { formatMileageSnapshotTime } from './data-freshness.js';
+
+test('formats snapshot instants in Asia/Shanghai', () => {
+  assert.equal(formatMileageSnapshotTime('2026-08-07T07:45:06.000Z'), '15:45:06');
+});
+
+test('keeps historical date snapshots explicit', () => {
+  assert.equal(formatMileageSnapshotTime('2026-08-06'), '2026-08-06');
+  assert.equal(formatMileageSnapshotTime(null), '--:--:--');
+});

src/modules/mileage/data-freshness.ts

@@ -0,0 +1,14 @@
+export function formatMileageSnapshotTime(value: string | null): string {
+  if (!value) return '--:--:--';
+  if (/^\d{4}-\d{2}-\d{2}$/.test(value)) return value;
+  const date = new Date(value);
+  if (Number.isNaN(date.getTime())) return value;
+  return new Intl.DateTimeFormat('zh-CN', {
+    timeZone: 'Asia/Shanghai',
+    hour: '2-digit',
+    minute: '2-digit',
+    second: '2-digit',
+    hour12: false,
+    hourCycle: 'h23',
+  }).format(date);
+}