go-shiori Server-Side Request Forgery via Unrestricted Bookmark URL Fetch

go-shiori's DownloadBookmark() (internal/core/download.go) fetches a caller-supplied bookmark URL using a plain http.Client with no custom DialContext or destination-IP validation (no IsLoopback(), IsPrivate(), IsUnspecified(), or IsLinkLocalUnicast() checks). An authenticated user creating or updating a bookmark via POST /api/bookmark, PUT /api/v1/bookmarks/cache, or POST /api/bookmarks/ext can supply a loopback (127.0.0.1) or 0.0.0.0 (which Linux redirects to loopback) URL, causing the server to make outbound requests to internal-only services, cloud metadata endpoints, or other network-restricted resources.