feat: show mining frame toast on OSD and speed up stats session deletes

- Flash mined-frame screenshot as in-overlay image toast for OSD card notifications
- Batch cover art from stored DB blobs via POST /api/stats/covers (no extra AniList fetches)
- Show delete progress toast on stats home and sessions pages
- Refresh only affected rollups on session delete instead of full rebuild
- Rebuild lifetime summaries with aggregate SQL CTEs instead of per-session loop

stats/src/components/anime/AnimeCoverImage.tsx

@@ -1,4 +1,4 @@
-import { useState } from 'react';
+import { RetryingCoverImage } from '../common/RetryingCoverImage';
 import { getStatsClient } from '../../hooks/useStatsApi';
 
 interface AnimeCoverImageProps {
@@ -8,28 +8,7 @@ interface AnimeCoverImageProps {
 }
 
 export function AnimeCoverImage({ animeId, title, className = '' }: AnimeCoverImageProps) {
-  const [failed, setFailed] = useState(false);
-  const fallbackChar = title.charAt(0) || '?';
-
-  if (failed) {
-    return (
-      <div
-        className={`bg-ctp-surface2 flex items-center justify-center text-ctp-overlay2 text-2xl font-bold ${className}`}
-      >
-        {fallbackChar}
-      </div>
-    );
-  }
-
   const src = getStatsClient().getAnimeCoverUrl(animeId);
 
-  return (
-    <img
-      src={src}
-      alt={title}
-      loading="lazy"
-      className={`object-cover bg-ctp-surface2 ${className}`}
-      onError={() => setFailed(true)}
-    />
-  );
+  return <RetryingCoverImage src={src} alt={title} fallbackLabel={title} className={className} />;
 }