feat: implement Iteration 0 foundation (backend + Flutter client)

Backend (Go):
- Project structure with chi router, pgxpool, goose migrations
- JWT auth (access/refresh tokens) with Firebase token verification
- NoopTokenVerifier for local dev without Firebase credentials
- PostgreSQL user repository with atomic profile updates (transactions)
- Mifflin-St Jeor calorie calculation based on profile data
- REST API: POST /auth/login, /auth/refresh, /auth/logout, GET/PUT /profile, GET /health
- Middleware: auth, CORS (localhost wildcard), logging, recovery, request_id
- Unit tests (51 passing) and integration tests (testcontainers)
- Docker Compose setup with postgres healthcheck and graceful shutdown

Flutter client:
- Riverpod state management with GoRouter navigation
- Firebase Auth (email/password + Google sign-in with web popup support)
- Platform-aware API URLs (web/Android/iOS)
- Dio HTTP client with JWT auth interceptor and concurrent refresh handling
- Secure token storage
- Screens: Login, Register, Home (tabs: Menu, Recipes, Products, Profile)
- Unit tests (17 passing)

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

client/test/shared/models/user_test.dart

@@ -0,0 +1,159 @@
+import 'package:flutter_test/flutter_test.dart';
+import 'package:food_ai/shared/models/user.dart';
+
+void main() {
+  group('User.fromJson', () {
+    test('deserializes full object', () {
+      final json = {
+        'id': 'user-1',
+        'email': 'test@example.com',
+        'name': 'Test User',
+        'avatar_url': 'https://avatar.url/pic.jpg',
+        'height_cm': 180,
+        'weight_kg': 75.5,
+        'age': 28,
+        'gender': 'male',
+        'activity': 'moderate',
+        'goal': 'maintain',
+        'daily_calories': 2500,
+        'plan': 'free',
+        'preferences': {'cuisines': ['russian']},
+      };
+
+      final user = User.fromJson(json);
+
+      expect(user.id, 'user-1');
+      expect(user.email, 'test@example.com');
+      expect(user.name, 'Test User');
+      expect(user.avatarUrl, 'https://avatar.url/pic.jpg');
+      expect(user.heightCm, 180);
+      expect(user.weightKg, 75.5);
+      expect(user.age, 28);
+      expect(user.gender, 'male');
+      expect(user.activity, 'moderate');
+      expect(user.goal, 'maintain');
+      expect(user.dailyCalories, 2500);
+      expect(user.plan, 'free');
+      expect(user.preferences['cuisines'], ['russian']);
+    });
+
+    test('deserializes minimal object (required fields only)', () {
+      final json = {
+        'id': 'user-2',
+        'email': 'min@example.com',
+        'name': 'Min User',
+        'plan': 'paid',
+      };
+
+      final user = User.fromJson(json);
+
+      expect(user.id, 'user-2');
+      expect(user.email, 'min@example.com');
+      expect(user.name, 'Min User');
+      expect(user.plan, 'paid');
+      expect(user.avatarUrl, isNull);
+      expect(user.heightCm, isNull);
+      expect(user.weightKg, isNull);
+      expect(user.age, isNull);
+      expect(user.gender, isNull);
+      expect(user.dailyCalories, isNull);
+      expect(user.preferences, isEmpty);
+    });
+
+    test('handles snake_case to camelCase mapping', () {
+      final json = {
+        'id': 'user-3',
+        'email': 'test@example.com',
+        'name': 'Test',
+        'plan': 'free',
+        'avatar_url': 'https://pic.url',
+        'height_cm': 170,
+        'weight_kg': 65.0,
+        'daily_calories': 2000,
+      };
+
+      final user = User.fromJson(json);
+
+      expect(user.avatarUrl, 'https://pic.url');
+      expect(user.heightCm, 170);
+      expect(user.weightKg, 65.0);
+      expect(user.dailyCalories, 2000);
+    });
+
+    test('roundtrip fromJson -> toJson -> fromJson', () {
+      final original = User(
+        id: 'user-4',
+        email: 'roundtrip@example.com',
+        name: 'Roundtrip',
+        avatarUrl: 'https://avatar.url',
+        heightCm: 175,
+        weightKg: 70.0,
+        age: 30,
+        gender: 'female',
+        activity: 'high',
+        goal: 'lose',
+        dailyCalories: 1800,
+        plan: 'paid',
+        preferences: {'cuisines': ['asian']},
+      );
+
+      final json = original.toJson();
+      final restored = User.fromJson(json);
+
+      expect(restored.id, original.id);
+      expect(restored.email, original.email);
+      expect(restored.name, original.name);
+      expect(restored.avatarUrl, original.avatarUrl);
+      expect(restored.heightCm, original.heightCm);
+      expect(restored.weightKg, original.weightKg);
+      expect(restored.age, original.age);
+      expect(restored.gender, original.gender);
+      expect(restored.plan, original.plan);
+      expect(restored.dailyCalories, original.dailyCalories);
+    });
+
+    test('ignores unknown fields', () {
+      final json = {
+        'id': 'user-5',
+        'email': 'test@example.com',
+        'name': 'Test',
+        'plan': 'free',
+        'unknown_field': 42,
+        'another_unknown': 'hello',
+      };
+
+      final user = User.fromJson(json);
+
+      expect(user.id, 'user-5');
+      expect(user.email, 'test@example.com');
+    });
+  });
+
+  group('User.hasCompletedOnboarding', () {
+    test('returns false when body params are missing', () {
+      const user = User(
+        id: '1',
+        email: 'test@test.com',
+        name: 'Test',
+        plan: 'free',
+      );
+
+      expect(user.hasCompletedOnboarding, isFalse);
+    });
+
+    test('returns true when all body params are present', () {
+      const user = User(
+        id: '1',
+        email: 'test@test.com',
+        name: 'Test',
+        plan: 'free',
+        heightCm: 180,
+        weightKg: 75.0,
+        age: 28,
+        gender: 'male',
+      );
+
+      expect(user.hasCompletedOnboarding, isTrue);
+    });
+  });
+}