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/utils/host-isolation.ts

@@ -24,6 +24,8 @@ export function shouldBlockImageHostRequest(
     requestHost?: string
     separationActive?: boolean
     imageHost?: string | null
+    siteHost?: string | null
+    hideFolder?: boolean
   }
 ): boolean {
   const separationActive = options?.separationActive ?? isDomainSeparationActive(event)
@@ -45,7 +47,45 @@ export function shouldBlockImageHostRequest(
   if (method !== 'GET' && method !== 'HEAD') return true
 
   const pathname = options?.pathname ?? requestUrl?.pathname ?? ''
+  const hideFolder = options?.hideFolder ?? isHideFolderInUrl(event)
   return requestPathToImageKey(pathname, {
-    hideFolder: isHideFolderInUrl(event)
+    hideFolder
   }) === null
 }
+
+/** 网站域禁止直链出图（仅图片域可 GET/HEAD 图片路径） */
+export function shouldBlockSiteHostImageRequest(
+  event: H3Event,
+  options?: {
+    method?: string
+    pathname?: string
+    requestHost?: string
+    separationActive?: boolean
+    siteHost?: string | null
+    hideFolder?: boolean
+  }
+): boolean {
+  const separationActive = options?.separationActive ?? isDomainSeparationActive(event)
+  if (!separationActive) return false
+
+  const siteHost = options?.siteHost ?? getConfiguredSiteHost(event)
+  if (!siteHost) return false
+
+  const requestUrl = options?.requestHost
+    ? null
+    : getRequestURL(event, {
+        xForwardedHost: true,
+        xForwardedProto: true
+      })
+  const requestHost = (options?.requestHost ?? requestUrl?.hostname ?? '').toLowerCase()
+  if (requestHost !== siteHost) return false
+
+  const method = (options?.method ?? getMethod(event)).toUpperCase()
+  if (method !== 'GET' && method !== 'HEAD') return false
+
+  const pathname = options?.pathname ?? requestUrl?.pathname ?? ''
+  const hideFolder = options?.hideFolder ?? isHideFolderInUrl(event)
+  return requestPathToImageKey(pathname, {
+    hideFolder
+  }) !== null
+}