feat: initial implementation — all 35 requirements across phases 1-3

Backend (Spring Boot 3.2 / Java 21 / PostgreSQL):
- JWT auth with BCrypt password hashing
- User profile + Mifflin-St Jeor BMR calculator
- Food search + barcode via OpenFoodFacts API with local cache
- Meal CRUD with user data isolation and ownership checks
- AI photo analysis (OpenAI Vision) with confidence intervals
- AI correction feedback loop for personalisation
- Flyway DB migrations + RFC-7807 error responses

Mobile (React Native / TypeScript):
- Full navigation stack (Auth → Tabs → Home stack)
- Design tokens (WCAG 2.2 AA colours, 8px grid, 48px touch targets)
- 10 screens: Login, Register, Home, Search, Camera, AI Result, Edit Meal,
  Daily Details, History, Profile
- Confidence-aware calorie display (kcal ± range)
- Repeat last meal shortcut + macro tracking

Docs:
- docs/PLAN-AND-REQUIREMENTS.md
- docs/traceability.csv (35 requirements, all Implemented)

mobile/App.tsx

@@ -0,0 +1,23 @@
+// Generated by GitHub Copilot
+import React, { useEffect, useState } from 'react';
+import AsyncStorage from '@react-native-async-storage/async-storage';
+import Navigator from './src/navigation/AppNavigator';
+
+/**
+ * App root — checks for a stored JWT to decide the initial navigation route.
+ */
+export default function App() {
+  const [isAuthenticated, setIsAuthenticated] = useState(false);
+  const [loading, setLoading] = useState(true);
+
+  useEffect(() => {
+    AsyncStorage.getItem('jwt_token').then(token => {
+      setIsAuthenticated(!!token);
+      setLoading(false);
+    });
+  }, []);
+
+  if (loading) return null;
+
+  return <Navigator isAuthenticated={isAuthenticated} />;
+}