feat: implement Iteration 6 — profile screen

Add ProfileService (GET/PUT /profile), ProfileNotifier provider,
and full ProfileScreen with body-params, goal/activity, daily-calories
sections and logout confirmation. EditProfileSheet lets user update
name, height, weight, age, gender, goal and activity; backend
auto-recalculates daily_calories via Mifflin-St Jeor.
HomeScreen greeting now shows the user's real name from profileProvider.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

client/lib/features/profile/profile_service.dart

@@ -0,0 +1,56 @@
+import 'package:flutter_riverpod/flutter_riverpod.dart';
+
+import '../../core/api/api_client.dart';
+import '../../core/auth/auth_provider.dart';
+import '../../shared/models/user.dart';
+
+final profileServiceProvider = Provider<ProfileService>((ref) {
+  return ProfileService(ref.read(apiClientProvider));
+});
+
+class UpdateProfileRequest {
+  final String? name;
+  final int? heightCm;
+  final double? weightKg;
+  final int? age;
+  final String? gender;
+  final String? activity;
+  final String? goal;
+
+  const UpdateProfileRequest({
+    this.name,
+    this.heightCm,
+    this.weightKg,
+    this.age,
+    this.gender,
+    this.activity,
+    this.goal,
+  });
+
+  Map<String, dynamic> toJson() {
+    final map = <String, dynamic>{};
+    if (name != null) map['name'] = name;
+    if (heightCm != null) map['height_cm'] = heightCm;
+    if (weightKg != null) map['weight_kg'] = weightKg;
+    if (age != null) map['age'] = age;
+    if (gender != null) map['gender'] = gender;
+    if (activity != null) map['activity'] = activity;
+    if (goal != null) map['goal'] = goal;
+    return map;
+  }
+}
+
+class ProfileService {
+  final ApiClient _client;
+  ProfileService(this._client);
+
+  Future<User> getProfile() async {
+    final json = await _client.get('/profile');
+    return User.fromJson(json);
+  }
+
+  Future<User> updateProfile(UpdateProfileRequest req) async {
+    final json = await _client.put('/profile', data: req.toJson());
+    return User.fromJson(json);
+  }
+}