feat: add smart-app-city sub-project architecture

- Architecture globale (React Native + NestJS + FastAPI)
- Beckn Protocol (OTN-DPI) integration docs
- AI layer: RAG pipeline + AI Agents (LocalAI + Qdrant)
- i18n: FR/EN/ES/DE support
- Docker Compose for backend services
- Project structure with frontend, backend, ai, beckn directories

smart-app-city/README.md

@@ -0,0 +1,61 @@
+# Smart App City — Mobile Application
+
+> Multi-platform mobile application for Smart City Digital Twin Martinique
+
+## Quick Start
+
+### Prerequisites
+- Node.js 20+
+- Expo CLI: `npm install -g expo-cli`
+- Docker & Docker Compose
+
+### Development
+
+```bash
+# Install dependencies
+cd frontend
+npm install
+
+# Start development server
+npx expo start
+
+# Run on device
+# Scan QR code with Expo Go app
+```
+
+### Backend
+
+```bash
+# Start all services
+cd ..
+docker-compose up -d
+
+# Start individual service
+cd backend/auth-service
+npm run start:dev
+```
+
+### AI Services
+
+```bash
+# Start RAG service
+cd ai/rag-service
+pip install -r requirements.txt
+uvicorn main:app --reload --port 8001
+
+# Start Agent service
+cd ai/agent-service
+pip install -r requirements.txt
+uvicorn main:app --reload --port 8002
+```
+
+## Documentation
+
+- [Architecture](docs/ARCHITECTURE.md)
+- [Beckn Integration](docs/BECKN_INTEGRATION.md)
+- [AI Architecture](docs/AI_ARCHITECTURE.md)
+- [Internationalization](docs/I18N.md)
+
+## License
+
+Smart City Digital Twin Martinique — Projet public