feat(web): desktop keyboard shortcuts

Space = play/pause, ←/→ = seek 5s, Shift+←/→ = prev/next, ↑/↓ = volume.
Handler lives in player.js (where _pos/_dur/seekToMs are in scope), wired
from startApp via initKeyboardShortcuts(). Ignored while typing in inputs,
and yields Space to focused buttons/links so it never double-fires.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

CHANGELOG.md

@@ -66,6 +66,7 @@ Versioning: two-part `MAJOR.MINOR` — each release bumps the minor (features an
 - **Android** — Duplicate-safe storage: a song shared by an album and a playlist is stored once (keyed by song ID) and reference-counted on delete — removing one group keeps the file if another still needs it
 - **Web + Android** — Lyrics prefetch: lyrics are fetched the moment a track starts playing (not only when the Lyrics tab is opened), so opening Lyrics is instant. The lrclib cache is warmed on every song change
 - **Web (PWA)** — Desktop install polish: `manifest.json` now ships PNG icons (192/512) for a crisp taskbar/Start-menu icon, drops the `portrait` lock so the window resizes freely, and adds a stable app `id` — installs as a standalone desktop window (no browser chrome)
+- **Web** — Keyboard shortcuts (desktop): Space = play/pause, ←/→ = seek 5 s, Shift+←/→ = previous/next track, ↑/↓ = volume. Ignored while typing in inputs/search fields
 
 ### Fixed
 - **Android** — Download crash on Android 15 (targetSdk 35): `FOREGROUND_SERVICE_TYPE_DATA_SYNC` is banned for apps targeting API 35; WorkManager's expedited path used it and the resulting exception killed the app ~1.5 s after tapping download. Fixed by dropping `setExpedited()` and all foreground-service use from `DownloadWorker` — downloads run as silent background work with progress shown in the Offline tab