Add Node.js/Express API service for booking backend

- New api/ service: Express + better-sqlite3, health check at GET /api/health,
  POST /api/bookings stores sessions with all required fields
- Dockerfile with Alpine build deps for native sqlite3 module
- docker-compose.yml: api service with volume mounts for data, signed-contracts, contracts
- nginx.conf: proxy /api/ to api:3001; Immich regex locations remain higher priority
- .gitignore: exclude SQLite db file and signed PDFs from version control

Closes #1

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

docker-compose.yml

@@ -25,12 +25,26 @@ services:
     networks:
       - web
 
-  # Optional: Watchtower for automatic updates
-  # watchtower:
-  #   image: containrrr/watchtower
-  #   volumes:
-  #     - /var/run/docker.sock:/var/run/docker.sock
-  #   command: --interval 300 lisilou-portfolio
+  api:
+    build:
+      context: ./api
+      dockerfile: Dockerfile
+    container_name: lisilou-api
+    restart: unless-stopped
+    env_file:
+      - ./api/.env
+    volumes:
+      - ./api/data:/app/data
+      - ./api/signed-contracts:/app/signed-contracts
+      - ./api/contracts:/app/contracts:ro
+    networks:
+      - web
+    healthcheck:
+      test: ["CMD", "wget", "--quiet", "--tries=1", "--spider", "http://localhost:3001/api/health"]
+      interval: 30s
+      timeout: 10s
+      retries: 3
+      start_period: 15s
 
 networks:
   web: