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>

.env.example

@@ -0,0 +1,56 @@
+# ============================================
+# Configuración del Sistema de Tracking de Trenes
+# ============================================
+# Copiar a .env y configurar según el entorno
+
+# ===========================================
+# DESARROLLO LOCAL
+# ===========================================
+
+# --- Base de Datos PostgreSQL ---
+POSTGRES_USER=trenes
+POSTGRES_PASSWORD=trenes_password_change_me
+POSTGRES_DB=trenes
+
+# --- Redis ---
+REDIS_PASSWORD=redis_password_change_me
+
+# --- Backend API ---
+JWT_SECRET=jwt_secret_change_me_min_32_chars
+CORS_ORIGINS=http://localhost,http://localhost:5173,http://localhost:3000
+LOG_LEVEL=info
+
+# --- Frontend ---
+# IMPORTANTE: Para desarrollo local
+VITE_API_URL=http://localhost/api
+VITE_WS_URL=http://localhost
+
+# --- Worker ---
+GTFS_RT_URL=https://gtfsrt.renfe.com/vehicle_positions.pb
+POLLING_INTERVAL=30000
+
+# --- Configuración de Entorno ---
+NODE_ENV=development
+
+# ===========================================
+# PRODUCCIÓN (ejemplo para trenes.millaguie.net)
+# ===========================================
+# Descomentar y ajustar para producción:
+#
+# POSTGRES_USER=trenes
+# POSTGRES_PASSWORD=<contraseña_segura_generada>
+# POSTGRES_DB=trenes
+#
+# JWT_SECRET=<secreto_jwt_largo_y_aleatorio>
+#
+# # IMPORTANTE: CORS_ORIGINS debe incluir tu dominio
+# CORS_ORIGINS=https://tudominio.com
+#
+# # IMPORTANTE sobre VITE_WS_URL:
+# # - Socket.io añade /socket.io/ automáticamente
+# # - NO incluir /ws o /socket.io en la URL
+# # - Usar https:// (no wss://), Socket.io maneja el protocolo
+# VITE_API_URL=https://tudominio.com/api
+# VITE_WS_URL=https://tudominio.com
+#
+# NODE_ENV=production