fix: reduce image provider timeout 120s→45s for faster fallback

При недоступности primary (aiguoguo) — быстрее переключаемся на
Nyxos fallback вместо ожидания 2 минуты.

src/services/covers.js

@@ -279,7 +279,7 @@ async function generateCoverViaImageGenerations({ prompt }) {
       const res = await axios.post(
         `${baseUrl}/images/generations`,
         { model, prompt: prompt.slice(0, 4000), n: 1, size: '1024x1024', response_format: 'url' },
-        { headers: { Authorization: `Bearer ${apiKey}` }, timeout: 120_000 }
+        { headers: { Authorization: `Bearer ${apiKey}` }, timeout: 45_000 }
       );
       const item = res.data?.data?.[0];
       if (!item) throw new Error('No image data in response');