feat: implement centralized access token management for media downloads and user authentication

src/app/components/message/FileHeader.tsx

@@ -12,6 +12,7 @@ import {
   downloadMedia,
   mxcUrlToHttp,
 } from '../../utils/matrix';
+import { getCurrentAccessToken } from '../../utils/auth';
 
 const badgeStyles = { maxWidth: toRem(100) };
 
@@ -28,7 +29,8 @@ export function FileDownloadButton({ filename, url, mimeType, encInfo }: FileDow
   const [downloadState, download] = useAsyncCallback(
     useCallback(async () => {
       const mediaUrl = mxcUrlToHttp(mx, url, useAuthentication) ?? url;
-      const accessToken = mx.getAccessToken();
+      // Always use current session's token to avoid stale tokens during account switches
+      const accessToken = getCurrentAccessToken();
       const fileContent = encInfo
         ? await downloadEncryptedMedia(mediaUrl, (encBuf) => decryptFile(encBuf, mimeType, encInfo), accessToken)
         : await downloadMedia(mediaUrl, accessToken);