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/serializers.py

@@ -46,10 +46,20 @@ class OrderSerializer(serializers.ModelSerializer):
         }
 
     def get_ingredients_summary(self, obj):
-        return obj.get_ingredients_summary()
+        # Compute in Python using prefetched dishes (avoids N+1)
+        summary = {}
+        for dish in obj.dishes.all():
+            for ing in dish.ingredients:
+                name = ing.get('name', '').strip()
+                amount = ing.get('amount', '').strip()
+                if name:
+                    if name in summary:
+                        if amount:
+                            summary[name] += f" + {amount}"
+                    else:
+                        summary[name] = amount
+        return [{'name': k, 'amount': v} for k, v in summary.items()]
 
-    def validate_dishes(self, value):
-        return value
 
     def create(self, validated_data):
         dish_ids = validated_data.pop('dish_ids', [])