fix(android player): seek broke after seamless track transitions (durationMs stuck at 0)

After skipping through already-buffered tracks the player stays READY, so
onPlaybackStateChanged never fires and syncState() isn't re-called; ctrl.duration
was TIME_UNSET(→0) at the transition, leaving state.durationMs stuck at 0. The
seek bar then computed fraction*0 = 0 and snapped playback to the start every time
(or to a stale value → "only 10s"). Restarting the app re-read the real duration,
which is why it recovered.

Fix: durationMs now self-heals — the 500ms ticker refreshes it too, and
resolveDurationMs() falls back to the current song's known duration while
ctrl.duration is still unset. Also record the Erkunden swipe-between-tabs idea.

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

CHANGELOG.md

@@ -453,6 +453,7 @@ Primary causes identified:
   - **New-release alerts:** periodic check for new albums/singles by followed artists (sources: iTunes lookup / MusicBrainz / Last.fm), surfaced in the existing in-app notification bell (and optionally push).
   - **Concert alerts:** reuse the existing **Ticketmaster** events integration to notify when a followed artist has nearby/upcoming shows.
   - Ties into the importer: a "download this new release" action straight from the notification.
+- **Android** — **Swipe between Erkunden sub-tabs** — a left/right swipe gesture on the Erkunden tab to switch between "Bibliothek" and "Global" search (instead of only tapping the chips). A fun, natural pager-style gesture (e.g. HorizontalPager).
 - **Android** — Playlist drag-and-drop / sort order
 - **Android** — Artist page iTunes fallback (for artists not in Navidrome)
 - **Android** — Romaji / Japanese sort support