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-auth.php

@@ -423,13 +423,21 @@ class TWP_Mobile_Auth {
         global $wpdb;
         $table = $wpdb->prefix . 'twp_mobile_sessions';
 
-        $wpdb->update(
-            $table,
-            array('fcm_token' => $fcm_token),
-            array('user_id' => $user_id, 'refresh_token' => $refresh_token, 'is_active' => 1),
-            array('%s'),
-            array('%d', '%s', '%d')
-        );
+        if (!empty($refresh_token)) {
+            $wpdb->update(
+                $table,
+                array('fcm_token' => $fcm_token),
+                array('user_id' => $user_id, 'refresh_token' => $refresh_token, 'is_active' => 1),
+                array('%s'),
+                array('%d', '%s', '%d')
+            );
+        } else {
+            // No refresh token — update the most recent active session for this user
+            $wpdb->query($wpdb->prepare(
+                "UPDATE $table SET fcm_token = %s WHERE user_id = %d AND is_active = 1 AND expires_at > NOW() ORDER BY created_at DESC LIMIT 1",
+                $fcm_token, $user_id
+            ));
+        }
     }
 
     /**