chore: add environment variable support and enhance startup script

- Add .env.example template for configurable Docker deployment settings
- Update docker-compose.yml to support environment-driven port/timezone configuration
- Refactor start.sh with improved Docker Compose detection, environment validation, and automated frontend building
- Enhance script documentation and error handling for better maintainability

docker-compose.yml

@@ -9,13 +9,13 @@ services:
     container_name: nofx-trading
     restart: unless-stopped
     ports:
-      - "8080:8080"
+      - "${NOFX_BACKEND_PORT:-8080}:8080"
     volumes:
       - ./config.json:/app/config.json:ro
       - ./decision_logs:/app/decision_logs
       - /etc/localtime:/etc/localtime:ro  # 同步主机时间
     environment:
-      - TZ=Asia/Shanghai  # 使用中国时区
+      - TZ=${NOFX_TIMEZONE:-Asia/Shanghai}  # 使用中国时区
     networks:
       - nofx-network
     healthcheck:
@@ -31,7 +31,7 @@ services:
     container_name: nofx-frontend
     restart: unless-stopped
     ports:
-      - "3000:80"
+      - "${NOFX_FRONTEND_PORT:-3000}:80"
     volumes:
       - ./web/dist:/usr/share/nginx/html:ro
       - ./nginx.conf:/etc/nginx/conf.d/default.conf:ro