fix(sync): 限流拦截不再把'上次同步'刷成现在 + 设置页新增立即同步按钮

- _set_sync_status 支持保留旧 last_sync_time；两处限流拦截(start_sync /
  sync_data)改为传旧值——被拒的同步零请求发生，不能把 UI 的'上次同步'
  拨快成'刚刚'，掩盖数据早已停更的事实
- SettingsPage 同步区块新增'立即同步'行：走 /garmin/sync-latest(最近2天，
  秒级阻塞返回)，成功/限流/未绑定三种状态都有明确反馈；限流中后端零请求
  拦截并回传恢复倒计时文案

backend/services/garmin.py

@@ -34,7 +34,15 @@ from services import garmin_extras as extras
 DEFAULT_SYNC_DAYS = int(os.environ.get("GARMIN_SYNC_DAYS") or 7)
 
 
-def _set_sync_status(user_id, status, now, **fields):
+def _set_sync_status(user_id, status, now, last_sync_time=None, **fields):
+    """Write the status row; `now` becomes the new last_sync_time by default.
+
+    Callers that merely *report* being blocked (a rate-limit refusal, a
+    refused start) pass the previous last_sync_time explicitly: a sync that
+    never happened must not move "上次同步" forward, or the UI reads "刚刚"
+    while the data actually stopped syncing hours ago.
+    """
+    last = last_sync_time if last_sync_time is not None else now
     cols = ["user_id", "status", "last_sync_time"] + list(fields.keys())
     placeholders = ", ".join(["?"] * len(cols))
     if DB_TYPE == "mariadb":
@@ -49,7 +57,7 @@ def _set_sync_status(user_id, status, now, **fields):
             f"INSERT INTO sync_status ({', '.join(cols)}) VALUES ({placeholders}) "
             f"ON CONFLICT(user_id) DO UPDATE SET {updates}"
         )
-    execute(sql, [user_id, status, now] + list(fields.values()))
+    execute(sql, [user_id, status, last] + list(fields.values()))
 
 
 def get_sync_status(user_id):
@@ -971,8 +979,15 @@ def start_sync(user_id, creds, days=None):
     now = datetime.datetime.utcnow().isoformat(timespec="seconds")
     until, msg = _rate_limit_block(user_id)
     if until:
+        # A refused start synced nothing — keep the previous last_sync_time so
+        # the UI's 上次同步 keeps telling the truth (the data is stale since
+        # the last *successful* sync, and that date is what the user needs).
+        row = query_one(
+            "SELECT last_sync_time FROM sync_status WHERE user_id = ?", [user_id]
+        )
         _set_sync_status(
             user_id, "rate_limited", now,
+            last_sync_time=row["last_sync_time"] if row else None,
             records_synced=0, progress_current=0, progress_total=days,
             started_at=now, last_error=msg,
         )
@@ -1005,9 +1020,14 @@ def sync_data(user_id, creds, days=None, client=None):
     until, msg = _rate_limit_block(user_id)
     if until:
         # A blocked account must issue zero Garmin requests — that is the whole
-        # point. Return immediately without touching the network.
+        # point. Return immediately without touching the network, and keep the
+        # previous last_sync_time (this was not a sync).
+        row = query_one(
+            "SELECT last_sync_time FROM sync_status WHERE user_id = ?", [user_id]
+        )
         _set_sync_status(
             user_id, "rate_limited", now,
+            last_sync_time=row["last_sync_time"] if row else None,
             records_synced=0, last_error=msg,
         )
         return {

client/src/pages/SettingsPage.tsx

@@ -29,6 +29,10 @@ function SettingsPage() {
   const [loading, setLoading] = useState(true);
   const [error, setError] = useState('');
   const [saved, setSaved] = useState('');
+  /** A sync is running right now (blocks the button). */
+  const [syncing, setSyncing] = useState(false);
+  /** A Garmin account is bound; sync-latest refuses to run without one. */
+  const [hasToken, setHasToken] = useState(false);
 
   useEffect(() => {
     Promise.all([apiClient.getSettings(), apiClient.getSettingsOptions()])
@@ -36,6 +40,8 @@ function SettingsPage() {
       .catch((err) => setError(errorMessage(err, '加载设置失败')))
       .finally(() => setLoading(false));
 
+    apiClient.getGarminAuthStatus().then(setHasToken).catch(() => setHasToken(false));
+
     if (FEATURES.ai) {
       apiClient.getModels().then(setModels).catch(() => setModels([]));
     }
@@ -64,6 +70,30 @@ function SettingsPage() {
     }
   };
 
+  /** 立即同步最近几天（秒级阻塞返回，不用进同步页）。
+      /garmin/sync-latest 只做最近 1-7 天的增量拉取，速度足够直接等待；
+      正在限流冷却时后端零请求直接拦截并返回恢复倒计时。 */
+  const syncNow = async () => {
+    setError('');
+    setSaved('');
+    setSyncing(true);
+    try {
+      const res = await apiClient.syncLatest(2);
+      if (res.status === 'rate_limited') {
+        setError(res.message || 'Garmin 正在限流，请耐心等待自动恢复。');
+      } else if (res.status === 'success') {
+        setSaved(res.message || '已同步最近数据');
+        window.setTimeout(() => setSaved(''), 3200);
+      } else {
+        setError(res.message || '同步没有完成，去同步页看具体原因。');
+      }
+    } catch (err: any) {
+      setError(errorMessage(err, '同步失败'));
+    } finally {
+      setSyncing(false);
+    }
+  };
+
   const pick = (
     title: string,
     values: Array<string | number>,
@@ -224,6 +254,24 @@ function SettingsPage() {
                 <span className="set-chevron" aria-hidden="true">›</span>
               </button>
 
+              <button
+                className="set-row"
+                onClick={syncNow}
+                disabled={syncing || !hasToken}
+              >
+                <span className="set-label">
+                  立即同步
+                  <span className="set-sub">
+                    {!hasToken
+                      ? '还没绑定 Garmin 账号，先在下面的「数据同步」里绑定'
+                      : '不等自动同步，马上拉取最近 2 天的数据'}
+                  </span>
+                </span>
+                <span className="set-value">
+                  {syncing ? '正在同步…' : ''}
+                </span>
+              </button>
+
               <Link href="/sync/" className="set-row">
                 <span className="set-label">
                   数据同步