Allow up to 40 candidate

app/routers/search.py

@@ -48,5 +48,5 @@ async def search_books(q: str = Query(...)):
     if dropped:
         logger.debug(f"🚮 truncated titles: {dropped[:10]}")
 
-    # Limit to 20 best matches
-    return merged[:20]
+    # Limit to 40 best matches
+    return merged[:40]