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/migrations/0008_remove_redundant_status_index.py

@@ -0,0 +1,18 @@
+# Generated by Django 5.2.11 on 2026-03-19 06:04
+
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('menu', '0007_add_indexes'),
+    ]
+
+    operations = [
+        migrations.AlterField(
+            model_name='order',
+            name='status',
+            field=models.CharField(choices=[('in_progress', '进行中'), ('completed', '已完成')], default='in_progress', max_length=20, verbose_name='状态'),
+        ),
+    ]