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/hooks/useAnimeLibrary.ts

@@ -1,4 +1,4 @@
-import { useState, useEffect } from 'react';
+import { useCallback, useState, useEffect } from 'react';
 import { getStatsClient } from './useStatsApi';
 import type { AnimeLibraryItem } from '../types/stats';
 
@@ -6,6 +6,11 @@ export function useAnimeLibrary() {
   const [anime, setAnime] = useState<AnimeLibraryItem[]>([]);
   const [loading, setLoading] = useState(true);
   const [error, setError] = useState<string | null>(null);
+  const [reloadToken, setReloadToken] = useState(0);
+
+  const reload = useCallback(() => {
+    setReloadToken((token) => token + 1);
+  }, []);
 
   useEffect(() => {
     let cancelled = false;
@@ -23,7 +28,7 @@ export function useAnimeLibrary() {
     return () => {
       cancelled = true;
     };
-  }, []);
+  }, [reloadToken]);
 
-  return { anime, loading, error };
+  return { anime, loading, error, reload };
 }