fix: never re-enable SSID pool broadcast (crash guard) + top-bar health chip

Mode 'active' and the advertise toggle could re-enable the SSID-pool
broadcast that segfaults pineapd. active preset now skips ssidpool/enable
(advertise stays false), the advertise endpoint refuses with an
explanation when the pool is disabled, get_ap reports the real pool
state, and the PineAP overview disables the toggle with a notice. Added
a top-bar health chip (PINEAP OK / POOL OFF / PINEAPD DOWN) polled every
15s.

payload/user/remote_access/pager-webui/www/js/app.js

@@ -434,6 +434,7 @@ const Live = (() => {
   let ws = null;
   let ever = false;
   let poll = null;
+  let pollHealthTimer = null;
   const subs = [];
   let timer = null;
   function stopPoll() {
@@ -442,6 +443,10 @@ const Live = (() => {
   function start() {
     if (ws && (ws.readyState === WebSocket.OPEN || ws.readyState === WebSocket.CONNECTING)) return;
     stopPoll();
+    if (!pollHealthTimer) {
+      pollHealthTimer = setInterval(pollHealth, 15000);
+      pollHealth();
+    }
     try { ws = new WebSocket(App.wsUrl('/api/ws')); }
     catch (e) { fallback(); return; }
     ws.onopen = () => { ever = true; };
@@ -489,6 +494,23 @@ const Live = (() => {
     const el = document.getElementById('live-status');
     if (el) el.textContent = 'BAT ' + (b.level == null ? '--' : b.level + '%' + (b.charging ? '+' : '')) + '  CLIENTS ' + n;
   }
+  function pollHealth() {
+    fetch(API_BASE + '/api/health', { credentials: 'include' }).then((r) => r.json())
+      .then((h) => {
+        const el = document.getElementById('health-status');
+        if (!el) return;
+        if (h.pineap_up === false) {
+          el.textContent = 'PINEAPD DOWN';
+          el.className = 'health-chip bad';
+        } else if (h.pool_disabled) {
+          el.textContent = 'POOL OFF';
+          el.className = 'health-chip warn';
+        } else if (h.pineap_up) {
+          el.textContent = 'PINEAP OK';
+          el.className = 'health-chip good';
+        }
+      }).catch(() => {});
+  }
   function onTick(fn) {
     subs.push(fn);
     return () => {