fix(consultations): open chat via consultation chat_id

Use chat_id from the consultations payload for direct navigation and keep
the chat lookup as a fallback for legacy rows without chat_id.

- validate chat id in ChatRepository and make it nullable
- guard repeated taps while opening chat
- handle nullable chat id in ProfileCubit and EmptyChatScreen

related to #1106

test/features/consultations/presentation/widgets/consultation_card_widget_test.dart

@@ -1,3 +1,5 @@
+import 'dart:async';
+
 import 'package:eatvio_app/core/app_config.dart';
 import 'package:eatvio_app/core/app_initializer.dart';
 import 'package:eatvio_app/core/locator_service.dart';
@@ -8,6 +10,7 @@ import 'package:eatvio_app/features/consultations/presentation/widgets/consultat
 import 'package:eatvio_app/features/plans/enums/chosen_plan_state_enum.dart';
 import 'package:eatvio_app/generated/l10n.dart';
 import 'package:flutter/material.dart';
+import 'package:flutter/services.dart';
 import 'package:flutter_bloc/flutter_bloc.dart';
 import 'package:flutter_dotenv/flutter_dotenv.dart';
 import 'package:flutter_localizations/flutter_localizations.dart';
@@ -33,6 +36,20 @@ void main() {
             AppConfig(buildType: AppBuildType.tests)
               ..setBaseUrl('http://localhost'),
       );
+
+      TestDefaultBinaryMessengerBinding.instance.defaultBinaryMessenger
+          .setMockMethodCallHandler(
+        const MethodChannel('PonnamKarthik/fluttertoast'),
+        (MethodCall methodCall) async => null,
+      );
+    });
+
+    tearDown(() {
+      TestDefaultBinaryMessengerBinding.instance.defaultBinaryMessenger
+          .setMockMethodCallHandler(
+        const MethodChannel('PonnamKarthik/fluttertoast'),
+        null,
+      );
     });
 
     final mockConsultation = ConsultationModel(
@@ -207,5 +224,93 @@ void main() {
         verify(() => cubit.getChatIdByUserSlug('john-doe')).called(1);
       });
     });
+
+    testWidgets(
+      'opens chat directly with chat id without requesting it again',
+      (tester) async {
+        final cubit = MockConsultationsCubit();
+        when(() => cubit.stream).thenAnswer((_) => const Stream.empty());
+        final consultationWithChatId = mockConsultation.copyWith(
+          chatId: 'direct-chat-uuid',
+        );
+
+        await mockNetworkImagesFor(() async {
+          await tester.pumpWidget(
+            wrap(
+              ConsultationCardWidget(
+                consultationsModel: consultationWithChatId,
+              ),
+              cubit: cubit,
+            ),
+          );
+          await tester.pumpAndSettle();
+
+          await tester.tap(find.byIcon(Icons.chat_outlined));
+          await tester.pumpAndSettle();
+
+          expect(find.text('chat:direct-chat-uuid'), findsOneWidget);
+          verifyNever(() => cubit.getChatIdByUserSlug(any()));
+        });
+      },
+    );
+
+    testWidgets('shows error and stays on card when chat id is null', (
+      tester,
+    ) async {
+      final cubit = MockConsultationsCubit();
+      when(() => cubit.stream).thenAnswer((_) => const Stream.empty());
+      when(() => cubit.getChatIdByUserSlug('john-doe'))
+          .thenAnswer((_) async => null);
+
+      await mockNetworkImagesFor(() async {
+        await tester.pumpWidget(
+          wrap(
+            ConsultationCardWidget(consultationsModel: mockConsultation),
+            cubit: cubit,
+          ),
+        );
+        await tester.pumpAndSettle();
+
+        await tester.tap(find.byIcon(Icons.chat_outlined));
+        await tester.pumpAndSettle();
+        await tester.pump(const Duration(seconds: 3));
+
+        expect(find.textContaining('chat:'), findsNothing);
+        expect(
+          find.byType(ConsultationCardWidget),
+          findsOneWidget,
+        );
+        verify(() => cubit.getChatIdByUserSlug('john-doe')).called(1);
+      });
+    });
+
+    testWidgets('does not request chat id twice while first is pending', (
+      tester,
+    ) async {
+      final cubit = MockConsultationsCubit();
+      when(() => cubit.stream).thenAnswer((_) => const Stream.empty());
+      final completer = Completer<String?>();
+      when(() => cubit.getChatIdByUserSlug('john-doe'))
+          .thenAnswer((_) => completer.future);
+
+      await mockNetworkImagesFor(() async {
+        await tester.pumpWidget(
+          wrap(
+            ConsultationCardWidget(consultationsModel: mockConsultation),
+            cubit: cubit,
+          ),
+        );
+        await tester.pumpAndSettle();
+
+        await tester.tap(find.byIcon(Icons.chat_outlined));
+        await tester.tap(find.byIcon(Icons.chat_outlined));
+
+        completer.complete('chat-uuid');
+        await tester.pumpAndSettle();
+
+        expect(find.text('chat:chat-uuid'), findsOneWidget);
+        verify(() => cubit.getChatIdByUserSlug('john-doe')).called(1);
+      });
+    });
   });
 }