feat: status page shows effective refresh mode across all active clients

- Server tracks each client's refresh rate via query param on /user-downloads
- Active clients expire after 30s of no requests
- Status panel 'Data Refresh' card shows:
  - Background poll interval (or Disabled)
  - Effective mode: Background if all clients >= poll rate,
    Foreground (with rate) if any client is faster, Idle if no clients
  - Active client list with per-user refresh rate and last-seen age
- Foreground mode shown with orange badge for visibility
- Client refresh rate sent on every dashboard request

server/routes/dashboard.js

@@ -90,6 +90,19 @@ function getRadarrLink(movie) {
   return `${movie._instanceUrl}/movie/${movie.titleSlug}`;
 }
 
+// Track active dashboard clients: Map<username, { refreshRateMs, lastSeen }>
+const activeClients = new Map();
+const CLIENT_STALE_MS = 30000; // consider client gone after 30s of no requests
+
+function getActiveClients() {
+  const now = Date.now();
+  // Prune stale clients
+  for (const [key, client] of activeClients.entries()) {
+    if (now - client.lastSeen > CLIENT_STALE_MS) activeClients.delete(key);
+  }
+  return Array.from(activeClients.values());
+}
+
 // Get user downloads for authenticated user
 router.get('/user-downloads', async (req, res) => {
   try {
@@ -106,6 +119,15 @@ router.get('/user-downloads', async (req, res) => {
     const showAll = isAdmin && req.query.showAll === 'true';
     console.log(`[Dashboard] Serving downloads for user: ${user.name} (${username}), isAdmin: ${isAdmin}, showAll: ${showAll}`);
 
+    // Track this client's refresh rate
+    const clientRefreshRate = parseInt(req.query.refreshRate, 10);
+    if (clientRefreshRate > 0) {
+      activeClients.set(username, { user: user.name, refreshRateMs: clientRefreshRate, lastSeen: Date.now() });
+    } else {
+      // Client has refresh off or didn't send — still mark as seen but with no rate
+      activeClients.set(username, { user: user.name, refreshRateMs: 0, lastSeen: Date.now() });
+    }
+
     // When polling is disabled, fetch on-demand if cache has expired
     // The fetched data is cached (30s TTL) so subsequent requests from any user reuse it
     if (!POLLING_ENABLED && !cache.get('poll:sab-queue')) {
@@ -628,7 +650,8 @@ router.get('/status', (req, res) => {
         intervalMs: POLLING_ENABLED ? require('../utils/poller').POLL_INTERVAL : 0,
         lastPoll: getLastPollTimings()
       },
-      cache: cacheStats
+      cache: cacheStats,
+      clients: getActiveClients()
     });
   } catch (err) {
     res.status(500).json({ error: 'Failed to get status', details: err.message });