Fix queue loading, null-safe models, autofill, and add outbound dialer

- Fix queue queries in mobile API and SSE to use twp_group_members
  (matching browser phone) instead of twp_queue_assignments
- Auto-create personal queues if user has no extension
- Make all model JSON parsing null-safe (handle null, string ints, bools)
- Add AutofillGroup and autofill hints to login form
- Add outbound calling with dialpad bottom sheet on dashboard

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

mobile/lib/services/voice_service.dart

@@ -62,6 +62,10 @@ class VoiceService {
     await TwilioVoice.instance.call.toggleSpeaker(speaker);
   }
 
+  Future<bool> makeCall(String to) async {
+    return await TwilioVoice.instance.call.place(to: to, from: _identity ?? '') ?? false;
+  }
+
   Future<void> sendDigits(String digits) async {
     await TwilioVoice.instance.call.sendDigits(digits);
   }