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

.env.example

@@ -0,0 +1,13 @@
+# NOFX Environment Variables Template
+# Copy this file to .env and modify the values as needed
+
+# Ports Configuration
+# Backend API server port (internal: 8080, external: configurable)
+NOFX_BACKEND_PORT=8080
+
+# Frontend web interface port (Nginx listens on port 80 internally)
+NOFX_FRONTEND_PORT=3000
+
+# Timezone Setting
+# System timezone for container time synchronization
+NOFX_TIMEZONE=Asia/Shanghai