fix(litellm): prefix EMBEDDING__MODEL with openai/ for litellm-pgvector

litellm.aembedding can't infer a provider from a bare model name plus a
custom api_base — litellm-pgvector's embedding_service.py was hitting
'litellm.BadRequestError: LLM Provider NOT provided' on every query-time
embedding (i.e. every search). Same openai/ prefix already used for
qwen3.8-27b-local and local-embedding in litellm-config.yaml.

docker-compose.yml

@@ -271,7 +271,11 @@ services:
       - SERVER_API_KEY=${LITELLM_PGVECTOR_API_KEY}
       # Calls back into litellm for embeddings, same pattern as any other
       # workload — see docs/proxy-key-onboarding.md for issuing this key.
-      - EMBEDDING__MODEL=local-embedding
+      # openai/ prefix required — litellm.aembedding can't infer a provider
+      # from a bare model name plus a custom api_base (raises "LLM Provider
+      # NOT provided"), same reasoning as the openai/ prefix on
+      # qwen3.8-27b-local and local-embedding in litellm-config.yaml.
+      - EMBEDDING__MODEL=openai/local-embedding
       - EMBEDDING__BASE_URL=http://litellm:4000
       - EMBEDDING__API_KEY=${LITELLM_PGVECTOR_EMBEDDING_KEY}
       - EMBEDDING__DIMENSIONS=768