fix(immich): use thumbnail endpoint instead of original for album carousel (#6396)

* fix(immich): use thumbnail endpoint instead of original for album carousel

Switches from /api/assets/:id/original to /api/assets/:id/thumbnail to fix
HEIC image incompatibility (thumbnails are always JPEG), reduce bandwidth,
and improve loading speed.

Closes #6388

* working on immich

* Improve image proxy error handling

* fix(image-proxy): use trusted fetch response type

* docs(immich): require Asset View permission

apps/docs/docs/integrations/immich/index.mdx

@@ -55,7 +55,7 @@ import { immichServerStatsWidget } from '../../widgets/immich-server-stats';
     <code>server.statistics</code>,{" "}
     <code>server.about</code>.
     <br />
-    Additional permissions may be required depending on your Immich version. If you encounter authorization errors, grant any missing permissions requested by the server.
+    The <strong>Asset View</strong> permission is required for the Immich Album Carousel to load image thumbnails. Select it when creating the API key, or use the <strong>All permissions</strong> preset. Without it, Immich returns a <code>403 Forbidden</code> response for thumbnail requests.
   </span>
 
 ),