feat: Initial commit - Train tracking system

Complete real-time train tracking system for Spanish railways (Renfe/Cercanías):

- Backend API (Node.js/Express) with GTFS-RT polling workers
- Frontend dashboard (React/Vite) with Leaflet maps
- Real-time updates via Socket.io WebSocket
- PostgreSQL/PostGIS database with Flyway migrations
- Redis caching layer
- Docker Compose configuration for development and production
- Gitea CI/CD workflows (lint, auto-tag, release)
- Production deployment with nginx + Let's Encrypt SSL

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

backend/.env.example

@@ -0,0 +1,20 @@
+# API Configuration
+PORT=3000
+NODE_ENV=development
+LOG_LEVEL=info
+
+# Database
+DATABASE_URL=postgresql://trenes_user:trenes_password@localhost:5432/trenes_db
+
+# Redis
+REDIS_URL=redis://:redis_password@localhost:6379
+
+# GTFS-RT
+GTFS_RT_URL=https://gtfsrt.renfe.com/vehicle_positions.pb
+POLLING_INTERVAL=30000
+
+# CORS
+CORS_ORIGIN=http://localhost:3000,http://localhost:5173
+
+# JWT
+JWT_SECRET=your_jwt_secret_here