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)

.gitignore

@@ -0,0 +1,29 @@
+# Backend build outputs
+backend/target/
+
+# Mobile
+mobile/node_modules/
+mobile/.gradle/
+mobile/android/build/
+mobile/ios/Pods/
+mobile/ios/build/
+
+# Environment & secrets — NEVER commit these
+.env
+.env.*
+*.env
+backend/src/main/resources/application-local.yml
+
+# IDE
+.idea/
+*.iml
+.vscode/settings.json
+*.class
+
+# OS
+.DS_Store
+Thumbs.db
+
+# Logs
+*.log
+logs/