chore(deploy): trim release retention and disable retrieval api key

Lower keep_releases default to 1 to reduce NAS disk usage, and clear
the bundled siliconflow retrieval api_key so deployments must supply
their own credentials.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

deploy/config.yaml

@@ -171,7 +171,7 @@ llm:
 retrieval:
   provider: siliconflow
   base_url: https://api.siliconflow.cn/v1
-  api_key: "sk-dikvcafrdcbajjpfgjjephqcggpdxwxdkighllieijlehwsf"
+  api_key: ‘’ #"sk-dikvcafrdcbajjpfgjjephqcggpdxwxdkighllieijlehwsf"
   embedding_model: BAAI/bge-m3
   reranker_model: BAAI/bge-reranker-v2-m3
   timeout: 30s