feat(garmin): 增加「退出 Garmin 账号」功能，删除已保存令牌以便重新登录

backend: services/garmin.py 新增 delete_token()，删除 garmin_tokens 行并 forget_client 丢弃缓存会话；routes/garmin.py 新增 POST /api/garmin/disconnect（require_auth），返回 ok + 提示文案。
frontend: api.ts 增加 disconnectGarmin()；SyncPage 增加「退出 Garmin 账号」按钮（带二次确认弹窗）；DataSync.css 增加危险色样式。
设计：仅删除 OAuth 令牌，保留 users.garmin_email，下次重登只需密码；已同步的健康数据不受影响。

backend/routes/garmin.py

@@ -56,6 +56,22 @@ def auth_status():
     return jsonify({"hasToken": garmin_svc.has_token(g.user_id)})
 
 
+@bp.route("/disconnect", methods=["POST"])
+@require_auth
+def disconnect():
+    """Drop the stored Garmin token so the next sync must re-authenticate.
+
+    Deletes the OAuth token (the UI calls this a "退出 Garmin 账号"). garmin_email
+    stays on the user record, so re-login only needs the password again. Already
+    synced health data is untouched.
+    """
+    garmin_svc.delete_token(g.user_id)
+    return jsonify({
+        "ok": True,
+        "message": "已退出 Garmin 账号，已保存的授权令牌已删除，下次同步需重新登录获取新令牌。",
+    })
+
+
 @bp.route("/login", methods=["POST"])
 @require_auth
 def login():

backend/services/garmin.py

@@ -257,6 +257,18 @@ def has_token(user_id):
     return load_token(user_id) is not None
 
 
+def delete_token(user_id):
+    """Forget the stored Garmin OAuth token.
+
+    The next sync or login will have to re-authenticate and mint a fresh token.
+    garmin_email on the user record is left in place so re-login only needs the
+    password. The cached client — built from the old token's session — is dropped
+    in the same step so a stale session can't keep being reused.
+    """
+    execute("DELETE FROM garmin_tokens WHERE user_id = ?", [user_id])
+    forget_client(user_id)
+
+
 # An authenticated client, reused across requests in this process.
 #
 # Building one costs ~11s against Garmin — loading the token, refreshing the

client/src/pages/DataSync.css

@@ -281,3 +281,21 @@
 }
 
 .sync-list li { margin-bottom: 0.2rem; }
+
+/* Account actions — destructive ones are flagged in red so they don't read
+   like the routine sync buttons above them. */
+.sync-account {
+  margin-top: 1.4rem;
+  padding-top: 1.1rem;
+  border-top: 1px solid var(--border);
+}
+
+.sync-disconnect {
+  color: var(--danger, #d23b3b);
+  border-color: var(--danger, #d23b3b);
+}
+
+.sync-disconnect:hover:not(:disabled) {
+  background: var(--danger, #d23b3b);
+  color: #fff;
+}

client/src/pages/SyncPage.tsx

@@ -164,6 +164,30 @@ function SyncPage() {
     setCodeSubmitted(false);
   };
 
+  // --- account ------------------------------------------------------------
+  /** Delete the stored Garmin token so the next sync forces a fresh login. */
+  const disconnect = async () => {
+    if (
+      !window.confirm(
+        '退出 Garmin 账号会删除已保存的授权令牌，下次同步需重新登录。确定继续？'
+      )
+    ) {
+      return;
+    }
+    setError('');
+    setMessage('');
+    setLoading(true);
+    try {
+      const res = await apiClient.disconnectGarmin();
+      setHasToken(false);
+      setMessage(res.message || '已退出 Garmin 账号，下次同步需重新登录获取新令牌。');
+    } catch (err: any) {
+      setError(errorMessage(err, '退出失败'));
+    } finally {
+      setLoading(false);
+    }
+  };
+
   // --- sync ---------------------------------------------------------------
 
   /** The last couple of days, awaited inline — seconds, not minutes. */
@@ -382,6 +406,19 @@ function SyncPage() {
                   </span>
                 </button>
               </div>
+
+              <div className="sync-account">
+                <button
+                  className="btn btn-plain sync-disconnect"
+                  onClick={disconnect}
+                  disabled={busy}
+                >
+                  退出 Garmin 账号
+                </button>
+                <p className="field-hint">
+                  删除已保存的授权令牌，下次同步需重新登录获取新令牌；已同步的数据不会丢失。
+                </p>
+              </div>
             </>
           )}
 

client/src/services/api.ts

@@ -467,6 +467,14 @@ class ApiClient {
     return data.hasToken;
   }
 
+  /** Drop the stored Garmin OAuth token; the next sync must re-authenticate. */
+  async disconnectGarmin() {
+    const { data } = await this.client.post<{ ok: boolean; message?: string }>(
+      '/garmin/disconnect'
+    );
+    return data;
+  }
+
   /**
    * Start an interactive Garmin login. Returns a session id; the login runs
    * in the background and parks if Garmin asks for a two-factor code.