chore(release): v0.22.0 — Download Center worker/sidecar in all composes + docs

Prep the Download Center epic (Phase 1 + editor + share) for prod/self-host:
- Dockerfile: create /downloads owned by appuser so a named-volume mount is writable (prod Linux).
- docker-compose.{home,selfhost,yml}: add the 'worker' (yt-dlp/ffmpeg job loop) + 'bgutil-pot'
  (PO-token) services + a downloads mount (DOWNLOAD_ROOT, WORKER_ENABLED). Media defaults to a
  named volume; DOWNLOAD_HOST_PATH points it at a host dir (e.g. a Plex-readable folder).
- README / docs/self-hosting.md / .env.example / install.{sh,ps1}: document the Download Center,
  the two extra containers, and DOWNLOAD_HOST_PATH.
- VERSION 0.22.0 + releaseNotes entry.

frontend/src/lib/releaseNotes.ts

@@ -14,6 +14,20 @@ export interface ReleaseEntry {
 }
 
 export const RELEASE_NOTES: ReleaseEntry[] = [
+  {
+    version: "0.22.0",
+    date: "2026-07-04",
+    summary: "The Download Center — save videos to the server, edit them into clips, and share them.",
+    features: [
+      "Download Center: save any video (or a search result) to the server with yt-dlp, laid out Plex-style with a poster + info file. Choose a built-in format preset or make your own, keep an eye on your per-user storage quota, and save the finished file to your device.",
+      "Built-in video editor: trim, crop, and cut a download into segments — keep the parts you want as separate clips or join them into one file. Pick a precise (frame-accurate) or fast cut, with a scrub timeline and a hover preview.",
+      "Sharing: share a download with another user (it appears in their “Shared with me”, where they can edit their own copy or remove it), or hand out a public watch link that plays on a clean, login-free page — with an optional password, an expiry, and a stream-only vs downloadable toggle.",
+      "Tidier video titles across the feed, search and downloads — clickbait ALL-CAPS and trailing hashtag clutter are cleaned up for display (the original title is kept underneath).",
+    ],
+    fixes: [
+      "The browser tab now carries an app icon and shows the section you're on; clicking the Siftlode logo returns you to the feed.",
+    ],
+  },
   {
     version: "0.21.0",
     date: "2026-07-02",