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/components/anime/AnimeHeader.tsx

@@ -6,6 +6,8 @@ interface AnimeHeaderProps {
   anilistEntries: AnilistEntry[];
   coverRetryToken?: number;
   onChangeAnilist?: () => void;
+  onDeleteAnime?: () => void;
+  isDeletingAnime?: boolean;
 }
 
 function AnilistButton({ entry }: { entry: AnilistEntry }) {
@@ -32,6 +34,8 @@ export function AnimeHeader({
   anilistEntries,
   coverRetryToken = 0,
   onChangeAnilist,
+  onDeleteAnime,
+  isDeletingAnime = false,
 }: AnimeHeaderProps) {
   const altTitles = [detail.titleRomaji, detail.titleEnglish, detail.titleNative].filter(
     (t): t is string => t != null && t !== detail.canonicalTitle,
@@ -95,6 +99,25 @@ export function AnimeHeader({
                 : 'Link to AniList'}
             </button>
           )}
+          {onDeleteAnime && (
+            <button
+              type="button"
+              onClick={onDeleteAnime}
+              disabled={isDeletingAnime}
+              title="Delete this title and every session and stat recorded for it"
+              className="inline-flex items-center gap-1 px-2 py-1 text-xs rounded bg-ctp-surface1 text-ctp-red/80 hover:bg-ctp-red/15 hover:text-ctp-red transition-colors disabled:opacity-50 disabled:cursor-not-allowed"
+            >
+              {isDeletingAnime ? (
+                <span
+                  aria-hidden="true"
+                  className="h-3 w-3 animate-spin rounded-full border-2 border-ctp-surface2 border-t-ctp-red"
+                />
+              ) : (
+                <span aria-hidden="true">{'\u2715'}</span>
+              )}
+              {isDeletingAnime ? 'Deleting\u2026' : 'Delete Entry'}
+            </button>
+          )}
         </div>
         {detail.description && (
           <p className="text-xs text-ctp-subtext0 mt-3 line-clamp-3 leading-relaxed">