feat(stats): add sentence search tab and fix mining card behavior

- Add Search tab with realtime subtitle sentence search, media context, and mining actions
- Persist library card size selection across reloads
- Fix selection text written only for sentence cards, not word/audio cards
- Fix word mining audio routed to SentenceAudio field when present
- Fix sentence card created immediately before slow media generation completes
- Fix Anki config resolved at request time for sentence mining
- Prefer non-Signs/Songs tracks when auto-selecting secondary subtitle language

stats/src/lib/stats-ui-navigation.test.tsx

@@ -10,6 +10,7 @@ test('TabBar renders Library instead of Anime for the media library tab', () =>
   assert.doesNotMatch(markup, />Anime</);
   assert.match(markup, />Overview</);
   assert.match(markup, />Library</);
+  assert.match(markup, />Search</);
 });
 
 test('EpisodeList renders explicit episode detail button alongside quick peek row', () => {