add API key protection

app/retrieval/reranker.py

@@ -166,7 +166,7 @@ async def warmup_reranker() -> bool:
     try:
         await _client.chat.completions.create(
             model=settings.groq_model,
-            messages=[{"role": "user", "content": 'Return {"test": 1}'}],
+            messages=[{"role": "user", "content": 'Return {"test": 1} in JSON format'}],
             temperature=0.0,
             max_tokens=10,
             response_format={"type": "json_object"}