feat(stats): add library entry deletion and app-wide delete progress

- Add "Delete Entry" to the anime detail view: removes every episode, session, subtitle line, rollup and cover art for a title plus the vocab counts derived from them, then drops it from the Library grid; refused while that title is currently playing.
- Show delete progress (session, session group, episode, entry) app-wide via a top progress bar + status toast that persist across tab switches, detail views, and the stats overlay window instead of going blank off-tab.
- Fix delete and Vocabulary-tab performance: store seen_ms on word/kanji occurrences so deletes subtract only removed rows via a covering index instead of rescanning each word's full history, and paginate vocab rows before aggregating anime counts.
- Migrate existing databases in place on first launch after upgrade.

stats/src/lib/delete-confirm.ts

@@ -60,6 +60,13 @@ export function confirmAnimeGroupDelete(title: string, count: number): Promise<b
   );
 }
 
+export function confirmAnimeDelete(title: string, episodeCount: number): Promise<boolean> {
+  const episodes = `${episodeCount} episode${episodeCount === 1 ? '' : 's'}`;
+  return confirmWithStatsNativeDialogLayer(
+    `Delete "${title}" from your library? This removes ${episodes} plus every session and stat recorded for them.`,
+  );
+}
+
 export function confirmEpisodeDelete(title: string): Promise<boolean> {
   return confirmWithStatsNativeDialogLayer(`Delete "${title}" and all its sessions?`);
 }