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>

scripts/dev-frontend.sh

@@ -0,0 +1,26 @@
+#!/bin/bash
+# ============================================================
+# dev-frontend.sh - 前端开发启动
+# 用法: ./scripts/dev-frontend.sh
+# 说明: 启动 Next.js 开发服务器，API 代理到后端
+# ============================================================
+set -e
+
+SCRIPT_DIR="$(cd "$(dirname "$0")" && pwd)"
+FRONTEND_DIR="$SCRIPT_DIR/../public-frontend"
+
+echo "=========================================="
+echo "  前端开发模式 - Next.js"
+echo "=========================================="
+echo ""
+echo "  后端 URL: ${BACKEND_URL:-http://127.0.0.1:5000}"
+echo "  访问: http://localhost:3000"
+echo "  Ctrl+C 停止"
+echo ""
+
+# 确保后端 URL 设置（默认本地）
+export BACKEND_URL=${BACKEND_URL:-http://127.0.0.1:5000}
+export NEXT_PUBLIC_BACKEND_URL=${BACKEND_URL}
+
+cd "$FRONTEND_DIR"
+exec npm run dev