Use backend endpoint for attachment downloads

src/components/messageStream/overlays/ImageLightbox.tsx

@@ -9,10 +9,9 @@ import {
 } from "react";
 import { createPortal } from "react-dom";
 import { ChevronLeft, ChevronRight, Download, X } from "lucide-react";
-import { postNoBody } from "../../../api";
 import type { Attachment } from "../../../types/post";
 import { autolink } from "../utils/autolink";
-import { downloadFile } from "../utils/downloadFile";
+import { downloadAttachment, downloadFile } from "../utils/downloadFile";
 
 type LightboxState = {
   images: Attachment[];
@@ -143,11 +142,12 @@ function LightboxView({
         onClick={(e) => {
           e.stopPropagation();
           if (postId) {
-            void postNoBody(
-              `/api/posts/${postId}/attachments/${current.id}/download`,
+            void downloadAttachment(postId, current.id, current.filename).catch(
+              () => {},
             );
+          } else {
+            void downloadFile(current.url, current.filename).catch(() => {});
           }
-          void downloadFile(current.url, current.filename).catch(() => {});
         }}
         className="absolute right-16 top-4 z-10 flex h-10 w-10 items-center justify-center rounded-full bg-white/10 text-white transition hover:bg-white/20"
         aria-label="Download"