fix(search): enrich missing SearXNG thumbnails with og:image

SearXNG liefert je nach Seite mal ein thumbnail/img_src mit, mal nicht —
bei Chefkoch-Treffern hatten deshalb zufällig die Hälfte der Kacheln
einen Platzhalter, obwohl die Vorschau dann sehr wohl ein Bild fand.

searchWeb() holt jetzt für jeden Treffer ohne Thumbnail parallel
(max. 6 gleichzeitig, 4 s Timeout pro Request) die Seite und extrahiert
das og:image- oder twitter:image-Meta-Tag. Ergebnis wird 30 min
in-memory gecacht, damit wiederholte Suchen nicht wieder die gleichen
Seiten laden.

Tests:
- Neuer Test: Treffer ohne Thumbnail wird via og:image angereichert.
- Neuer Test: Treffer mit Thumbnail bleibt unverändert (keine Fetch).
- Bestehende Tests deaktivieren Enrichment via enrichThumbnails:false,
  damit sie keine echten Chefkoch-URLs aufrufen.

src/lib/server/search/searxng.ts

@@ -77,10 +77,61 @@ function looksLikeRecipePage(url: string): boolean {
   }
 }
 
+const OG_IMAGE_RE =
+  /<meta[^>]+(?:property|name)=["']og:image(?::url)?["'][^>]+content=["']([^"']+)["']/i;
+const OG_IMAGE_RE_REV =
+  /<meta[^>]+content=["']([^"']+)["'][^>]+(?:property|name)=["']og:image(?::url)?["']/i;
+const TWITTER_IMAGE_RE =
+  /<meta[^>]+(?:property|name)=["']twitter:image["'][^>]+content=["']([^"']+)["']/i;
+
+function extractOgImage(html: string): string | null {
+  const m = OG_IMAGE_RE.exec(html) ?? OG_IMAGE_RE_REV.exec(html) ?? TWITTER_IMAGE_RE.exec(html);
+  if (!m) return null;
+  try {
+    return new URL(m[1]).toString();
+  } catch {
+    return null;
+  }
+}
+
+type ThumbCacheEntry = { image: string | null; expires: number };
+const thumbCache = new Map<string, ThumbCacheEntry>();
+const THUMB_TTL_MS = 30 * 60 * 1000;
+
+async function enrichThumbnail(url: string): Promise<string | null> {
+  const now = Date.now();
+  const cached = thumbCache.get(url);
+  if (cached && cached.expires > now) return cached.image;
+  let image: string | null = null;
+  try {
+    const html = await fetchText(url, { timeoutMs: 4_000, maxBytes: 256 * 1024 });
+    image = extractOgImage(html);
+  } catch {
+    image = null;
+  }
+  thumbCache.set(url, { image, expires: now + THUMB_TTL_MS });
+  return image;
+}
+
+async function enrichMissingThumbnails(hits: WebHit[]): Promise<void> {
+  const queue = hits.filter((h) => !h.thumbnail);
+  if (queue.length === 0) return;
+  const LIMIT = 6;
+  const workers = Array.from({ length: Math.min(LIMIT, queue.length) }, async () => {
+    while (queue.length > 0) {
+      const h = queue.shift();
+      if (!h) break;
+      const image = await enrichThumbnail(h.url);
+      if (image) h.thumbnail = image;
+    }
+  });
+  await Promise.all(workers);
+}
+
 export async function searchWeb(
   db: Database.Database,
   query: string,
-  opts: { searxngUrl?: string; limit?: number } = {}
+  opts: { searxngUrl?: string; limit?: number; enrichThumbnails?: boolean } = {}
 ): Promise<WebHit[]> {
   const trimmed = query.trim();
   if (!trimmed) return [];
@@ -131,5 +182,8 @@ export async function searchWeb(
     });
     if (hits.length >= limit) break;
   }
+  if (opts.enrichThumbnails !== false) {
+    await enrichMissingThumbnails(hits);
+  }
   return hits;
 }

tests/integration/searxng.test.ts

@@ -42,7 +42,7 @@ describe('searchWeb', () => {
         content: 'blocked'
       }
     ]);
-    const hits = await searchWeb(db, 'carbonara', { searxngUrl: baseUrl });
+    const hits = await searchWeb(db, 'carbonara', { searxngUrl: baseUrl, enrichThumbnails: false });
     expect(hits.length).toBe(1);
     expect(hits[0].domain).toBe('chefkoch.de');
     expect(hits[0].title).toBe('Carbonara');
@@ -55,23 +55,60 @@ describe('searchWeb', () => {
       { url: 'https://www.chefkoch.de/a', title: 'A', content: '' },
       { url: 'https://www.chefkoch.de/a', title: 'A dup', content: '' }
     ]);
-    const hits = await searchWeb(db, 'a', { searxngUrl: baseUrl });
+    const hits = await searchWeb(db, 'a', { searxngUrl: baseUrl, enrichThumbnails: false });
     expect(hits.length).toBe(1);
   });
 
   it('returns empty list when no domains configured', async () => {
     const db = openInMemoryForTest();
-    const hits = await searchWeb(db, 'x', { searxngUrl: baseUrl });
+    const hits = await searchWeb(db, 'x', { searxngUrl: baseUrl, enrichThumbnails: false });
     expect(hits).toEqual([]);
   });
 
   it('returns empty for empty query', async () => {
     const db = openInMemoryForTest();
     addDomain(db, 'chefkoch.de');
-    const hits = await searchWeb(db, '   ', { searxngUrl: baseUrl });
+    const hits = await searchWeb(db, '   ', { searxngUrl: baseUrl, enrichThumbnails: false });
     expect(hits).toEqual([]);
   });
 
+  it('enriches missing thumbnails from og:image', async () => {
+    const pageServer = createServer((_req, res) => {
+      res.writeHead(200, { 'content-type': 'text/html; charset=utf-8' });
+      res.end(
+        '<html><head><meta property="og:image" content="https://cdn.example/foo.jpg" /></head><body></body></html>'
+      );
+    });
+    await new Promise<void>((r) => pageServer.listen(0, '127.0.0.1', r));
+    const addr = pageServer.address() as AddressInfo;
+    const pageUrl = `http://127.0.0.1:${addr.port}/rezept`;
+    try {
+      const db = openInMemoryForTest();
+      addDomain(db, '127.0.0.1');
+      respondWith([{ url: pageUrl, title: 'Kuchen', content: '' }]);
+      const hits = await searchWeb(db, 'kuchen', { searxngUrl: baseUrl });
+      expect(hits.length).toBe(1);
+      expect(hits[0].thumbnail).toBe('https://cdn.example/foo.jpg');
+    } finally {
+      await new Promise<void>((r) => pageServer.close(() => r()));
+    }
+  });
+
+  it('leaves existing thumbnails untouched (no enrichment fetch)', async () => {
+    const db = openInMemoryForTest();
+    addDomain(db, 'chefkoch.de');
+    respondWith([
+      {
+        url: 'https://www.chefkoch.de/rezepte/1/x.html',
+        title: 'X',
+        thumbnail: 'https://cdn.chefkoch/x.jpg'
+      }
+    ]);
+    // enrichment enabled, but thumbnail is set → no fetch expected, no hang
+    const hits = await searchWeb(db, 'x', { searxngUrl: baseUrl });
+    expect(hits[0].thumbnail).toBe('https://cdn.chefkoch/x.jpg');
+  });
+
   it('filters out forum/magazine/listing URLs', async () => {
     const db = openInMemoryForTest();
     addDomain(db, 'chefkoch.de');
@@ -83,7 +120,7 @@ describe('searchWeb', () => {
       { url: 'https://www.chefkoch.de/themen/ravioli/', title: 'Themen' },
       { url: 'https://www.chefkoch.de/rezepte/', title: 'Rezepte Übersicht' }
     ]);
-    const hits = await searchWeb(db, 'ravioli', { searxngUrl: baseUrl });
+    const hits = await searchWeb(db, 'ravioli', { searxngUrl: baseUrl, enrichThumbnails: false });
     expect(hits.length).toBe(1);
     expect(hits[0].title).toBe('Ravioli');
   });