Show visible SSE live status with last update time on dashboard.

Co-authored-by: Cursor <cursoragent@cursor.com>

app/templates/dashboard.html

@@ -1,7 +1,10 @@
 {% extends "base.html" %}
 {% block title %}总览 · {{ app_name }}{% endblock %}
 {% block content %}
-<h2 style="margin:0 0 14px">总览 <span class="muted" style="font-size:13px;font-weight:400" id="live-hint">· 秒级推送</span></h2>
+<h2 style="margin:0 0 14px;display:flex;align-items:center;gap:10px;flex-wrap:wrap">
+  总览
+  <span id="live-hint" class="tag" style="font-size:12px;font-weight:500">连接中…</span>
+</h2>
 <div class="grid cols-3">
   <div class="card"><div class="muted">账户</div><div class="stat">{{ accounts|length }}</div></div>
   <div class="card">
@@ -78,6 +81,29 @@
   var liveUrl = {{ url_for('dashboard_live')|tojson }};
   var detailBase = {{ url_for('record_detail', tid=0)|tojson }}.replace(/0$/, '');
   var hint = document.getElementById('live-hint');
+  var mode = 'connecting';
+  var pollStarted = false;
+  var msgCount = 0;
+
+  function pad(n) { return n < 10 ? '0' + n : String(n); }
+  function nowClock() {
+    var d = new Date();
+    return pad(d.getHours()) + ':' + pad(d.getMinutes()) + ':' + pad(d.getSeconds());
+  }
+
+  function setHint(text, kind) {
+    if (!hint) return;
+    hint.textContent = text;
+    hint.className = 'tag' + (kind ? ' ' + kind : '');
+  }
+
+  function markUpdated() {
+    if (mode === 'sse') {
+      setHint('SSE · 更新于 ' + nowClock(), 'green');
+    } else if (mode === 'poll') {
+      setHint('轮询 1s · 更新于 ' + nowClock(), '');
+    }
+  }
 
   function esc(s) {
     return String(s == null ? '' : s)
@@ -136,30 +162,46 @@
     document.getElementById('stat-online').textContent = String(data.online_count);
     renderMachines(data.online_machines || []);
     renderTrades(data.trades || []);
+    markUpdated();
   }
 
-  function startPollFallback() {
+  function startPollFallback(reason) {
-    if (hint) hint.textContent = '· 轮询 1s（SSE 不可用）';
+    if (pollStarted) return;
+    pollStarted = true;
+    mode = 'poll';
+    setHint(reason || '轮询 1s（SSE 不可用）', '');
     setInterval(function () {
       fetch(liveUrl, { credentials: 'same-origin' })
         .then(function (r) { return r.json(); })
         .then(apply)
-        .catch(function () {});
+        .catch(function () { setHint('轮询失败 · 重试中', 'red'); });
     }, 1000);
   }
 
   if (typeof EventSource === 'undefined') {
-    startPollFallback();
+    startPollFallback('轮询 1s（浏览器不支持 SSE）');
     return;
   }
 
+  setHint('SSE 连接中…', '');
   var es = new EventSource(streamUrl);
+  es.onopen = function () {
+    mode = 'sse';
+    setHint('SSE 已连接', 'green');
+  };
   es.onmessage = function (ev) {
+    msgCount += 1;
+    mode = 'sse';
     try { apply(JSON.parse(ev.data)); } catch (e) {}
   };
   es.onerror = function () {
-    es.close();
+    // 已收到过数据则让浏览器自行重连；长时间无数据再降级轮询
-    startPollFallback();
+    if (msgCount === 0 || es.readyState === EventSource.CLOSED) {
+      try { es.close(); } catch (e) {}
+      startPollFallback('轮询 1s（SSE 断开）');
+    } else {
+      setHint('SSE 重连中…', '');
+    }
   };
 })();
 </script>