Fix Android crash: don't register push without Firebase

On Android, PushNotifications.register() calls FirebaseMessaging.getInstance(),
which throws "Default FirebaseApp is not initialized" when the build has no
google-services.json. Capacitor runs the plugin method on its own thread, so the
exception is an UNCAUGHT NATIVE crash a JS try/catch can't stop — the app died
right after sign-in and on every relaunch.

Gate Android push registration on a new server flag: /api/meetings/config now
returns fcm (push.fcmReady() = FCM_SERVICE_ACCOUNT present). setupNativePush skips
register() on Android unless fcm is true. Web-side fix — deploys without a rebuild;
push auto-enables once Firebase (client google-services.json + server FCM) is set up.
iOS/APNs unchanged.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

server/push.js

@@ -179,6 +179,10 @@ console.log(enabled.length ? '[push] enabled: ' + enabled.join(', ') : '[push] d
 
 function isEnabled() { return webReady; }      // Web Push specifically (drives /api/push/vapid)
 function publicKey() { return webReady ? PUBLIC : ''; }
+// Whether Android FCM is configured on the server. The Android app must NOT call PushNotifications.register()
+// unless Firebase is set up (client google-services.json + this) — otherwise it throws "Default FirebaseApp is
+// not initialized", an uncaught NATIVE crash. The web uses this flag to gate Android push registration.
+function fcmReady() { return !!fcmSA; }
 
 // Fire-and-forget to every channel the user has: Web Push subscriptions + native device
 // tokens. Dead endpoints/tokens are pruned. Never throws.
@@ -207,4 +211,4 @@ async function sendToUser(userId, payload) {
   }
 }
 
-module.exports = { isEnabled, publicKey, sendToUser, sendCallNotification, sendCallCancel };
+module.exports = { isEnabled, publicKey, sendToUser, sendCallNotification, sendCallCancel, fcmReady };