feat: add admin-only status page with cache stats

- New /api/dashboard/status endpoint (admin-only, 403 for non-admins)
- Returns server info (uptime, Node version, memory usage)
- Returns polling mode and interval
- Returns cache stats: entry count, total size, per-key breakdown
  with item count, size in KB, and TTL remaining
- Status button in admin controls header
- Collapsible status panel with grid layout
- Responsive: single column on mobile

server/routes/dashboard.js

@@ -600,4 +600,38 @@ router.get('/user-summary', async (req, res) => {
   }
 });
 
+// Admin-only status page with cache stats
+router.get('/status', (req, res) => {
+  try {
+    const userCookie = req.cookies.emby_user;
+    if (!userCookie) {
+      return res.status(401).json({ error: 'Not authenticated' });
+    }
+    const user = JSON.parse(userCookie);
+    if (!user.isAdmin) {
+      return res.status(403).json({ error: 'Admin access required' });
+    }
+
+    const cacheStats = cache.getStats();
+    const uptime = process.uptime();
+
+    res.json({
+      server: {
+        uptimeSeconds: Math.floor(uptime),
+        nodeVersion: process.version,
+        memoryUsageMB: Math.round(process.memoryUsage().rss / 1024 / 1024 * 10) / 10,
+        heapUsedMB: Math.round(process.memoryUsage().heapUsed / 1024 / 1024 * 10) / 10,
+        heapTotalMB: Math.round(process.memoryUsage().heapTotal / 1024 / 1024 * 10) / 10
+      },
+      polling: {
+        enabled: POLLING_ENABLED,
+        intervalMs: POLLING_ENABLED ? require('../utils/poller').POLL_INTERVAL : 0
+      },
+      cache: cacheStats
+    });
+  } catch (err) {
+    res.status(500).json({ error: 'Failed to get status', details: err.message });
+  }
+});
+
 module.exports = router;