perf: 性能与资源优化 - 提取内联资源、数据库查询优化、限流与缓存增强

主要优化:
- templates/index.html: 220KB → 28KB，内联CSS/JS提取为静态文件
- menu/serializers.py: 修复 Order.ingredients_summary N+1 查询问题
- menu/services/dish_service.py: 移除多余查询，添加 only() 限制字段
- menu/views.py: 上传接口添加每分钟20次限流
- static/js/api.js: 统一API错误处理
- zhangmenu/settings.py: 添加Whitenoise压缩、Redis缓存支持、环境变量配置
- static/css/app.css, static/js/app.js: 提取的内联资源文件
- 新增 migrations, requirements.txt, .env.example

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

menu/services/dish_service.py

@@ -8,7 +8,10 @@ class DishService:
     @staticmethod
     def get_queryset(category_id=None, search=None):
         """获取菜品查询集"""
-        queryset = Dish.objects.select_related('category')
+        queryset = Dish.objects.select_related('category').only(
+            'id', 'name', 'category', 'category__name', 'cover_image',
+            'description', 'ingredients', 'view_count', 'created_at', 'updated_at'
+        )
 
         if category_id:
             queryset = queryset.filter(category_id=category_id)
@@ -21,5 +24,3 @@ class DishService:
     def increment_view_count(dish):
         """增加浏览次数"""
         Dish.objects.filter(pk=dish.pk).update(view_count=F('view_count') + 1)
-        dish.refresh_from_db(fields=['view_count'])
-        return dish