Remove outdated Flutter migration documents and add new technical descriptions and profile repository implementation

- Deleted `next_steps_flutter.md` and `teknisk_beskrivning_flutter.md` files as they were outdated.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/presentation/profile_screen.dart

@@ -1,12 +1,122 @@
 import 'package:flutter/material.dart';
+import 'package:flutter_riverpod/flutter_riverpod.dart';
+import '../../../core/api/api_error_mapper.dart';
+import '../../data/profile_repository.dart';
 
-class ProfileScreen extends StatelessWidget {
+class ProfileScreen extends ConsumerStatefulWidget {
   const ProfileScreen({super.key});
 
+  @override
+  ConsumerState<ProfileScreen> createState() => _ProfileScreenState();
+}
+
+class _ProfileScreenState extends ConsumerState<ProfileScreen> {
+  final _formKey = GlobalKey<FormState>();
+  String _username = '';
+  String _email = '';
+  bool _isLoading = true;
+
+  @override
+  void initState() {
+    super.initState();
+    _loadProfile();
+  }
+
+  Future<void> _loadProfile() async {
+    try {
+      final profile = await ref.read(profileRepositoryProvider).getProfile();
+      setState(() {
+        _username = profile['username'] ?? '';
+        _email = profile['email'] ?? '';
+        _isLoading = false;
+      });
+    } catch (e) {
+      _showErrorMessage(e);
+      setState(() {
+        _isLoading = false;
+      });
+    }
+  }
+
+  Future<void> _updateProfile() async {
+    if (_formKey.currentState!.validate()) {
+      _formKey.currentState!.save();
+      setState(() {
+        _isLoading = true;
+      });
+      try {
+        await ref.read(profileRepositoryProvider).updateProfile({
+          'username': _username,
+          'email': _email,
+        });
+        ScaffoldMessenger.of(context).showSnackBar(
+          const SnackBar(content: Text('Profil uppdaterad!')),
+        );
+      } catch (e) {
+        _showErrorMessage(e);
+      } finally {
+        setState(() {
+          _isLoading = false;
+        });
+      }
+    }
+  }
+
+  void _showErrorMessage(dynamic error) {
+    final message = mapErrorToUserMessage(error, context);
+    ScaffoldMessenger.of(context).showSnackBar(
+      SnackBar(content: Text(message)),
+    );
+  }
+
   @override
   Widget build(BuildContext context) {
-    return const Center(
-      child: Text('Profilsida (grundversion)'),
+    return Scaffold(
+      appBar: AppBar(
+        title: const Text('Användarprofil'),
+      ),
+      body: _isLoading
+          ? const Center(child: CircularProgressIndicator())
+          : Padding(
+              padding: const EdgeInsets.all(16.0),
+              child: Form(
+                key: _formKey,
+                child: Column(
+                  children: <Widget>[
+                    TextFormField(
+                      decoration: const InputDecoration(labelText: 'Användarnamn'),
+                      initialValue: _username,
+                      validator: (value) {
+                        if (value == null || value.isEmpty) {
+                          return 'Ange ett användarnamn';
+                        }
+                        return null;
+                      },
+                      onSaved: (value) => _username = value!,
+                    ),
+                    TextFormField(
+                      decoration: const InputDecoration(labelText: 'E-post'),
+                      initialValue: _email,
+                      validator: (value) {
+                        if (value == null || value.isEmpty) {
+                          return 'Ange en e-postadress';
+                        }
+                        if (!RegExp(r'^[^@]+@[^@]+\.[^@]+').hasMatch(value)) {
+                          return 'Ange en giltig e-postadress';
+                        }
+                        return null;
+                      },
+                      onSaved: (value) => _email = value!,
+                    ),
+                    const SizedBox(height: 20),
+                    ElevatedButton(
+                      onPressed: _updateProfile,
+                      child: const Text('Spara'),
+                    ),
+                  ],
+                ),
+              ),
+            ),
     );
   }
 }