Remove outdated Flutter migration documents and add new technical descriptions and profile repository implementation

- Deleted `next_steps_flutter.md` and `teknisk_beskrivning_flutter.md` files as they were outdated.
- Added new `next_steps_flutter.md` and `teknisk_beskrivning_flutter.md` files with updated migration plans and technical descriptions for the Flutter frontend.
- Implemented `profile_repository.dart` to handle profile data retrieval and updates using the API.

Co-authored-by: Copilot <copilot@github.com>

flutter/lib/features/profile/data/profile_repository.dart

@@ -0,0 +1,27 @@
+import 'package:flutter_riverpod/flutter_riverpod.dart';
+import '../../../core/api/api_client.dart';
+import '../../../core/api/guarded_api_call.dart';
+import '../../../core/api/api_exception.dart';
+
+final profileRepositoryProvider = Provider<ProfileRepository>((ref) {
+  final apiClient = ref.read(apiClientProvider);
+  return ProfileRepository(apiClient);
+});
+
+class ProfileRepository {
+  final ApiClient _apiClient;
+
+  ProfileRepository(this._apiClient);
+
+  Future<Map<String, dynamic>> getProfile() async {
+    return guardedApiCall(
+      () => _apiClient.getJson('/api/profile'),
+    );
+  }
+
+  Future<Map<String, dynamic>> updateProfile(Map<String, dynamic> profileData) async {
+    return guardedApiCall(
+      () => _apiClient.patchJson('/api/profile', profileData),
+    );
+  }
+}