已有同步任务时直接显示进度条，不再弹阻塞提示

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

ft-app/app/templates/admin.html

@@ -267,11 +267,9 @@ function startSync(url) {
     .then(function(r) { return r.json(); })
     .then(function(data) {
       if (!data.ok) {
-        document.getElementById('sync-progress-label').textContent = '已有同步任务进行中，请稍后再试';
-        document.getElementById('sync-progress-pct').textContent = '';
-        document.getElementById('sync-progress-bar').style.width = '0%';
-        document.getElementById('sync-progress').insertAdjacentHTML('beforeend',
-          '<button onclick="hideProgress()" style="display:block;margin-top:10px;padding:4px 14px;border:1px solid var(--border);border-radius:5px;background:var(--surface);color:var(--fg);cursor:pointer;font-size:0.8rem;">关闭</button>');
+        // Another sync is already running — just show its progress
+        syncTimer = setInterval(pollProgress, 500);
+        pollProgress();
         return;
       }
       syncTimer = setInterval(pollProgress, 500);