fix(share): use the stable YouTube hqdefault thumbnail for OG on YT shares (0.57.1)

Facebook's scraper rejected our self-hosted poster as "Corrupted Image": the poster is an
ffmpeg-produced JPEG (non-standard marker order) that browsers/iOS/Twitter decode fine but FB's
stricter processor won't. For a YouTube source, point og:image at the video's stable, non-expiring
`i.ytimg.com/vi/<id>/hqdefault.jpg` (a Google-encoded JPEG FB decodes reliably) built from the id in
the stored thumbnail — instead of the stored `sqp`-signed variant, which can expire. Non-YouTube
sources keep the poster fallback (fine everywhere but FB). Declares 480×360 so FB includes it on the
first async scrape. og.py only — no schema change.

frontend/src/lib/releaseNotes.ts

@@ -14,6 +14,13 @@ export interface ReleaseEntry {
 }
 
 export const RELEASE_NOTES: ReleaseEntry[] = [
+  {
+    version: "0.57.1",
+    date: "2026-07-28",
+    fixes: [
+      "Sharing: a YouTube video's shared-link preview now uses the original YouTube thumbnail, which Facebook Messenger reliably shows — the previously-served self-hosted image was a valid picture everywhere else but Facebook's stricter processor rejected it as “corrupted”.",
+    ],
+  },
   {
     version: "0.57.0",
     date: "2026-07-28",