fix(ml): restrict cross-encoder batch_size to prevent OOM kills on uncapped arrays

backend/src/ml/reranker.py

@@ -17,7 +17,8 @@ def rerank(query: str, passages: list[str]) -> list[float]:
         return []
     reranker = _get_reranker()
     pairs = [[query, p] for p in passages]
-    scores = reranker.compute_score(pairs, normalize=True)
+    # Enforce small batch_size to prevent OOM kills on 100+ candidates in cloud environments
+    scores = reranker.compute_score(pairs, normalize=True, batch_size=8)
     if isinstance(scores, float):
         scores = [scores]
     return [float(s) for s in scores]