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/providers/call_provider.dart

@@ -103,6 +103,15 @@ class CallProvider extends ChangeNotifier {
 
   Future<void> sendDigits(String digits) => _voiceService.sendDigits(digits);
 
+  Future<void> makeCall(String number) async {
+    _callInfo = _callInfo.copyWith(
+      state: CallState.connecting,
+      callerNumber: number,
+    );
+    notifyListeners();
+    await _voiceService.makeCall(number);
+  }
+
   Future<void> holdCall() async {
     final sid = _callInfo.callSid;
     if (sid == null) return;