feat: Implement DataErrorHandler mixin and update imports for consistency

apps/mobile/packages/data_connect/lib/src/services/data_connect_service.dart

@@ -6,7 +6,7 @@ import 'package:krow_core/core.dart';
 import 'package:krow_domain/krow_domain.dart';
 
 import '../../krow_data_connect.dart' as dc;
-import '../mixins/data_error_handler.dart';
+import 'mixins/data_error_handler.dart';
 
 /// A centralized service for interacting with Firebase Data Connect.
 ///

apps/mobile/packages/data_connect/lib/src/services/mixins/data_error_handler.dart

@@ -0,0 +1,71 @@
+import 'dart:async';
+import 'dart:io';
+
+import 'package:firebase_core/firebase_core.dart';
+import 'package:flutter/material.dart';
+import 'package:krow_domain/krow_domain.dart';
+
+/// Mixin to handle Data Layer errors and map them to Domain Failures.
+///
+/// Use this in Repositories to wrap remote calls.
+/// It catches [SocketException], [FirebaseException], etc., and throws [AppException].
+mixin DataErrorHandler {
+  /// Executes a Future and maps low-level exceptions to [AppException].
+  ///
+  /// [timeout] defaults to 30 seconds.
+  Future<T> executeProtected<T>(
+    Future<T> Function() action, {
+    Duration timeout = const Duration(seconds: 30),
+  }) async {
+    try {
+      return await action().timeout(timeout);
+    } on TimeoutException {
+      throw ServiceUnavailableException(
+          technicalMessage: 'Request timed out after ${timeout.inSeconds}s');
+    } on SocketException catch (e) {
+      throw NetworkException(technicalMessage: 'SocketException: ${e.message}');
+    } on FirebaseException catch (e) {
+      final String code = e.code.toLowerCase();
+      final String msg = (e.message ?? '').toLowerCase();
+      if (code == 'unavailable' ||
+          code == 'network-request-failed' ||
+          msg.contains('offline') ||
+          msg.contains('network') ||
+          msg.contains('connection failed')) {
+        throw NetworkException(
+            technicalMessage: 'Firebase ${e.code}: ${e.message}');
+      }
+      if (code == 'deadline-exceeded') {
+        throw ServiceUnavailableException(
+            technicalMessage: 'Firebase ${e.code}: ${e.message}');
+      }
+      // Fallback for other Firebase errors
+      throw ServerException(
+          technicalMessage: 'Firebase ${e.code}: ${e.message}');
+    } catch (e) {
+      final String errorStr = e.toString().toLowerCase();
+      if (errorStr.contains('socketexception') ||
+          errorStr.contains('network') ||
+          errorStr.contains('offline') ||
+          errorStr.contains('connection failed') ||
+          errorStr.contains('unavailable') ||
+          errorStr.contains('handshake') ||
+          errorStr.contains('clientexception') ||
+          errorStr.contains('failed host lookup') ||
+          errorStr.contains('connection error') ||
+          errorStr.contains('grpc error') ||
+          errorStr.contains('terminated') ||
+          errorStr.contains('connectexception')) {
+        throw NetworkException(technicalMessage: e.toString());
+      }
+      
+      // If it's already an AppException, rethrow it
+      if (e is AppException) rethrow;
+
+      // Debugging: Log unexpected errors
+      debugPrint('DataErrorHandler: Unhandled exception caught: $e');
+      
+      throw UnknownException(technicalMessage: e.toString());
+    }
+  }
+}