feat(scrobble stats): navigator lower bound, clickable rows, android button to top

- Navigator can't step before logging began: the endpoint returns firstPlayedAt
  (MIN(played_at) over all the user's plays, unfiltered by window); web + android
  disable the back arrow once the shown year/month is at/before that first play.
- Top artists/tracks/albums are now clickable → open the artist / album page (web
  navigates and closes the overlay; android navigates via nav routes). Tracks open
  their album.
- Android: moved the 'Meine Statistiken' button to the top of Settings (was at the
  bottom near logout). SW cache -> ns-v70.

Android compileDebugKotlin + web build green; firstPlayedAt verified server-side.

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

public/sw.js

@@ -1,4 +1,4 @@
-const CACHE = 'ns-v69';
+const CACHE = 'ns-v70';
 const PRECACHE = ['/', 'index.html', 'manifest.json', 'icon.svg'];
 const SKIP_PATHS = ['/rest/stream', '/rest/download', '/config.js'];
 // Auth token params stripped from cache keys so artwork survives across sessions/token refreshes.