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/api/settings/index.patch.ts

@@ -5,6 +5,7 @@ import {
   setSetting,
   SETTINGS_ALLOWED_REFERER_HOSTS,
   SETTINGS_HIDE_FOLDER_IN_URL,
+  SETTINGS_STORAGE_USE_DATE_PATH,
   SETTINGS_IMAGE_BASE_URL,
   SETTINGS_SITE_BASE_URL,
   SETTINGS_WEBP_QUALITY,
@@ -31,6 +32,7 @@ interface SettingsPatchBody {
   siteBaseUrl?: unknown
   imageBaseUrl?: unknown
   hideFolderInUrl?: unknown
+  storageUseDatePath?: unknown
   autoDeleteDays?: unknown
   allowRegistration?: unknown
 }
@@ -135,5 +137,9 @@ export default defineEventHandler(async (event) => {
     setSetting(SETTINGS_HIDE_FOLDER_IN_URL, body.hideFolderInUrl ? 'true' : 'false')
   }
 
+  if (body.storageUseDatePath !== undefined) {
+    setSetting(SETTINGS_STORAGE_USE_DATE_PATH, body.storageUseDatePath ? 'true' : 'false')
+  }
+
   return getSettingsPayload(event)
 })