feat: storage path layout, basename URLs, and bidirectional domain isolation

Add storage_use_date_path for flat vs date-key storage layout and emit
basename-only public URLs when hide-folder is enabled. Block image paths
on the site host when domain separation is active so only the image host
serves files. Update settings UI, i18n, tests, and deployment docs.

server/middleware/01-serve-image.ts

@@ -1,7 +1,7 @@
 import { requestPathToImageKey, serveImageByKey } from '../utils/serve-image'
 
 /**
- * 仅当路径像图片 key（{type}/YYYY/MM/file.ext）时才接管。
+ * 仅当路径像图片 key 或短链时才接管。
  * 其它请求（/_nuxt、/api、页面）原样放行。
  */
 export default defineEventHandler(async (event) => {