refactor(server): 移除鉴权并归档遗留路由至 legacy/

- 删除 auth.py 与 deps.py，各路由去除 get_current_user 依赖
- collection.py 更名为 materials.py，冻结链路（ozon/publish/shops/categories）移入 legacy/
- 扩展默认生图服务端口并入 8800 并自动迁移旧配置，水印默认文案改为 Panda Store
- 新增 docs/v2.1/backend-structure.md 后端结构盘点文档

studio/src/services/suite.ts

@@ -80,7 +80,7 @@ export interface WatermarkPayload {
 export const DEFAULT_WATERMARK: WatermarkPayload = {
     enabled: false,
     type: 'text',
-    text: 'xiongmaoyx',
+    text: 'Panda Store',
     opacity: 30,
 };