Add FCM push notifications, queue alerts, caller ID fixes, and auto-revert agent status

Server-side:
- Add push credential auto-creation for FCM incoming call notifications
- Add queue alert FCM notifications (data-only for background delivery)
- Add queue alert cancellation on call accept/disconnect
- Fix caller ID to show caller's number instead of Twilio number
- Fix FCM token storage when refresh_token is null
- Add pre_call_status tracking to revert agent status 30s after call ends
- Add SSE fallback polling for mobile app connectivity

Mobile app:
- Add Android telecom permissions and phone account registration
- Add VoiceFirebaseMessagingService for incoming call push handling
- Add insistent queue alert notifications with custom sound
- Fix caller number display on active call screen
- Add caller ID selection dropdown on dashboard
- Add phone numbers endpoint and provider support
- Add unit tests for CallInfo, QueueState, and CallProvider
- Remove local.properties from tracking, add .gitignore

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

includes/class-twp-mobile-sse.php

@@ -26,14 +26,32 @@ class TWP_Mobile_SSE {
                 'callback' => array($this, 'stream_events'),
                 'permission_callback' => array($this->auth, 'verify_token')
             ));
+            register_rest_route('twilio-mobile/v1', '/stream/poll', array(
+                'methods' => 'GET',
+                'callback' => array($this, 'poll_state'),
+                'permission_callback' => array($this->auth, 'verify_token')
+            ));
         });
     }
 
+    /**
+     * Return current state as JSON (polling alternative to SSE)
+     */
+    public function poll_state($request) {
+        $user_id = $this->auth->get_current_user_id();
+        if (!$user_id) {
+            return new WP_Error('unauthorized', 'Invalid token', array('status' => 401));
+        }
+        return rest_ensure_response($this->get_current_state($user_id));
+    }
+
     /**
      * Stream events to mobile app
      */
     public function stream_events($request) {
+        error_log('TWP SSE: stream_events called');
         $user_id = $this->auth->get_current_user_id();
+        error_log('TWP SSE: user_id=' . ($user_id ?: 'false'));
 
         if (!$user_id) {
             return new WP_Error('unauthorized', 'Invalid token', array('status' => 401));
@@ -56,6 +74,15 @@ class TWP_Mobile_SSE {
             ob_end_flush();
         }
 
+        // Flush padding to overcome Apache/HTTP2 frame buffering.
+        // SSE comments (lines starting with ':') are ignored by clients.
+        // We send >4KB to ensure the first HTTP/2 DATA frame is flushed.
+        echo ':' . str_repeat(' ', 4096) . "\n\n";
+        if (ob_get_level() > 0) ob_flush();
+        flush();
+
+        error_log('TWP SSE: padding flushed, sending connected event');
+
         // Send initial connection event
         $this->send_event('connected', array('user_id' => $user_id, 'timestamp' => time()));