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>

mobile/test/call_info_test.dart

@@ -0,0 +1,129 @@
+import 'package:flutter_test/flutter_test.dart';
+import 'package:twp_softphone/models/call_info.dart';
+
+void main() {
+  group('CallInfo', () {
+    test('default state is idle', () {
+      const info = CallInfo();
+      expect(info.state, CallState.idle);
+      expect(info.callSid, isNull);
+      expect(info.callerNumber, isNull);
+      expect(info.duration, Duration.zero);
+      expect(info.isMuted, false);
+      expect(info.isSpeakerOn, false);
+      expect(info.isOnHold, false);
+    });
+
+    test('isActive returns true for ringing, connecting, connected', () {
+      expect(const CallInfo(state: CallState.ringing).isActive, true);
+      expect(const CallInfo(state: CallState.connecting).isActive, true);
+      expect(const CallInfo(state: CallState.connected).isActive, true);
+    });
+
+    test('isActive returns false for idle and disconnected', () {
+      expect(const CallInfo(state: CallState.idle).isActive, false);
+      expect(const CallInfo(state: CallState.disconnected).isActive, false);
+    });
+
+    test('copyWith preserves unmodified fields', () {
+      const original = CallInfo(
+        state: CallState.connected,
+        callSid: 'CA123',
+        callerNumber: '+1234567890',
+        isMuted: true,
+      );
+
+      final modified = original.copyWith(isSpeakerOn: true);
+      expect(modified.state, CallState.connected);
+      expect(modified.callSid, 'CA123');
+      expect(modified.callerNumber, '+1234567890');
+      expect(modified.isMuted, true);
+      expect(modified.isSpeakerOn, true);
+    });
+
+    test('copyWith can change state', () {
+      const info = CallInfo(state: CallState.connecting);
+      final updated = info.copyWith(state: CallState.connected);
+      expect(updated.state, CallState.connected);
+    });
+
+    test('copyWith with callerNumber preserves it', () {
+      const info = CallInfo(callerNumber: '+19095737372');
+      final updated = info.copyWith(state: CallState.connected);
+      expect(updated.callerNumber, '+19095737372');
+    });
+
+    test('reset to idle clears all fields', () {
+      // Verify a complex state exists
+      const connected = CallInfo(
+        state: CallState.connected,
+        callSid: 'CA123',
+        callerNumber: '+1234567890',
+        isMuted: true,
+        isSpeakerOn: true,
+        isOnHold: true,
+        duration: Duration(seconds: 30),
+      );
+      expect(connected.isActive, true);
+
+      // Simulating what callEnded does
+      const reset = CallInfo();
+      expect(reset.state, CallState.idle);
+      expect(reset.callSid, isNull);
+      expect(reset.callerNumber, isNull);
+      expect(reset.isActive, false);
+    });
+  });
+
+  group('CallState transitions', () {
+    test('outbound call flow: idle -> connecting -> connected -> idle', () {
+      var info = const CallInfo();
+      expect(info.state, CallState.idle);
+
+      // makeCall sets connecting + callerNumber
+      info = info.copyWith(state: CallState.connecting, callerNumber: '+19095737372');
+      expect(info.state, CallState.connecting);
+      expect(info.callerNumber, '+19095737372');
+      expect(info.isActive, true);
+
+      // SDK fires connected
+      info = info.copyWith(state: CallState.connected);
+      expect(info.state, CallState.connected);
+      expect(info.callerNumber, '+19095737372'); // preserved
+      expect(info.isActive, true);
+
+      // callEnded resets
+      info = const CallInfo();
+      expect(info.state, CallState.idle);
+      expect(info.isActive, false);
+    });
+
+    test('inbound call flow: idle -> ringing -> connected -> idle', () {
+      var info = const CallInfo();
+
+      info = info.copyWith(state: CallState.ringing);
+      expect(info.isActive, true);
+
+      // callerNumber set from active.from
+      info = info.copyWith(callerNumber: '+18005551234');
+      expect(info.callerNumber, '+18005551234');
+
+      info = info.copyWith(state: CallState.connected);
+      expect(info.state, CallState.connected);
+
+      info = const CallInfo();
+      expect(info.state, CallState.idle);
+    });
+
+    test('outbound callerNumber not overwritten by null copyWith', () {
+      var info = const CallInfo(
+        state: CallState.connecting,
+        callerNumber: '+19095737372',
+      );
+
+      // copyWith without callerNumber should preserve it
+      info = info.copyWith(state: CallState.connected);
+      expect(info.callerNumber, '+19095737372');
+    });
+  });
+}