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/Dockerfile

@@ -0,0 +1,86 @@
+# Multi-stage Dockerfile para Backend (API + Worker)
+FROM node:20-alpine AS base
+
+# Instalar dependencias del sistema
+RUN apk add --no-cache \
+    python3 \
+    make \
+    g++ \
+    curl \
+    wget
+
+WORKDIR /app
+
+# Copiar archivos de dependencias
+COPY package*.json ./
+
+# Instalar dependencias
+RUN npm install --omit=dev && \
+    npm cache clean --force
+
+# Copiar código fuente
+COPY . .
+
+# ================================
+# Stage para API
+# ================================
+FROM base AS api
+
+ENV NODE_ENV=production
+ENV PORT=3000
+
+# Crear usuario no-root
+RUN addgroup -g 1001 -S nodejs && \
+    adduser -S nodejs -u 1001
+
+USER nodejs
+
+EXPOSE 3000
+
+# Health check
+HEALTHCHECK --interval=30s --timeout=10s --start-period=40s --retries=3 \
+    CMD wget --quiet --tries=1 --spider http://localhost:3000/health || exit 1
+
+CMD ["node", "src/api/server.js"]
+
+# ================================
+# Stage para Worker
+# ================================
+FROM base AS worker
+
+ENV NODE_ENV=production
+
+# Crear usuario no-root
+RUN addgroup -g 1001 -S nodejs && \
+    adduser -S nodejs -u 1001
+
+USER nodejs
+
+# Health check para worker (verifica que el proceso esté corriendo)
+HEALTHCHECK --interval=60s --timeout=10s --start-period=40s --retries=3 \
+    CMD pgrep -f "node.*worker" || exit 1
+
+CMD ["node", "src/worker/gtfs-poller.js"]
+
+# ================================
+# Stage de desarrollo (opcional)
+# ================================
+FROM node:20-alpine AS development
+
+RUN apk add --no-cache \
+    python3 \
+    make \
+    g++ \
+    curl \
+    wget
+
+WORKDIR /app
+
+COPY package*.json ./
+RUN npm install
+
+COPY . .
+
+ENV NODE_ENV=development
+
+CMD ["npm", "run", "dev"]