Refactor infrastructure scripts and add mock hardware support

Changes:
- Refactor project scripts for better dev/prod workflow separation
- Add mock_hardware.py for local development without real hardware
- Add Makefile for common commands
- Add .env.example for environment variable reference
- Split scripts into dev-backend.sh, dev-frontend.sh, prod-backend.sh
- Add stop.sh for clean shutdown

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

.env.example

@@ -0,0 +1,21 @@
+# 环境变量配置示例
+# 复制此文件为 .env 并修改需要的值
+
+# ========== 开发模式 ==========
+# 设置为 1 启用 Mock 硬件模式（本地开发，无需真实硬件）
+MOCK_HARDWARE=0
+
+# ========== 后端配置 ==========
+FLASK_PORT=5000
+
+# ========== 前端配置 ==========
+# 前端开发服务器会代理 API 请求到后端
+BACKEND_URL=http://127.0.0.1:5000
+
+# ========== 硬件配置（生产环境） ==========
+AGV_HOST=192.168.60.80
+ARM_HOST=192.168.60.120
+
+# ========== 外部 API ==========
+# TEST_MODE: true=测试环境, false=正式环境
+TEST_MODE=false