The Android app updates itself from our Gitea releases; feed cards fade in instead of bouncing

- API: GET /app/android/latest reads the latest Gitea release (ANDROID_RELEASES_URL, optional token for a
  private repo) with the APK's SHA-256 from SHA256SUMS; GET /app/android/apk/:name streams that APK.
- App (modules/updater): downloads in the background, checks the SHA-256, and installs through
  PackageInstaller: quietly once when leaving the app (Android 12+), otherwise from the feed banner or
  Settings > App version. F-Droid builds leave it out and drop the install permissions.
- CI: the release notes come from the fastlane changelog; the app shows the part above ---.
- Settings: Create-account and Link Spotify buttons for Last.fm and ListenBrainz.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

apps/api/src/env.ts

@@ -34,6 +34,13 @@ const schema = z.object({
     .string()
     .default('https://lrclib.net')
     .transform((v) => v.replace(/\/+$/, '')),
+  /**
+   * App updates: the Gitea/Forgejo API URL of the latest Android release, e.g.
+   * https://gitea.example.com/api/v1/repos/owner/musicshare/releases/latest. Empty turns update checks off.
+   * The token (read access to the repo) is only needed when the repo is private; downloads go through us.
+   */
+  ANDROID_RELEASES_URL: z.string().default(''),
+  ANDROID_RELEASES_TOKEN: optional,
   /** Apple Music (MusicKit): Team ID, MusicKit key ID, and the key's .p8 contents (newlines may be written as \n). */
   APPLE_TEAM_ID: optional,
   APPLE_MUSICKIT_KEY_ID: optional,