Fix mobile app: AccessToken for voice, Agent Manager for status, caller ID support

- Voice token: use AccessToken + VoiceGrant instead of browser-only ClientToken
- Agent status: delegate to TWP_Agent_Manager matching browser phone behavior
- Queue loading: add missing require_once for TWP_User_Queue_Manager
- Add /phone-numbers endpoint for caller ID selection
- Webhook: support CallerId param from mobile extraOptions
- Flutter: caller ID dropdown in dialer, error logging in all catch blocks

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

mobile/lib/providers/call_provider.dart

@@ -103,13 +103,13 @@ class CallProvider extends ChangeNotifier {
 
   Future<void> sendDigits(String digits) => _voiceService.sendDigits(digits);
 
-  Future<void> makeCall(String number) async {
+  Future<void> makeCall(String number, {String? callerId}) async {
     _callInfo = _callInfo.copyWith(
       state: CallState.connecting,
       callerNumber: number,
     );
     notifyListeners();
-    await _voiceService.makeCall(number);
+    await _voiceService.makeCall(number, callerId: callerId);
   }
 
   Future<void> holdCall() async {