fix(litellm): add missing api_key to vector_store_registry

Without it, litellm's pg_vector provider sent Authorization: Bearer None,
which round-tripped to the real api.openai.com and came back with
'Incorrect API key provided: None' — masking the actual problem and making
every vector store call fail. Points at litellm-pgvector's own
LITELLM_PGVECTOR_API_KEY (its SERVER_API_KEY), already present in .env.

Smoke-tested end-to-end against the live deploy for issue #24, alongside
the litellm-pgvector fixes in the following commits.

litellm-config.yaml

@@ -53,16 +53,27 @@ search_tools:
 # Qdrant — LiteLLM's native vector-store feature has no Qdrant provider, see
 # docs/research/litellm-knowledgebase.md). vector_store_id is this proxy's
 # own identifier for the store, not assigned by a backend.
-# ponytail: field names here (custom_llm_provider: pg_vector, api_base
-# pointed at litellm-pgvector) are the best fit from the litellm-pgvector
-# README, not confirmed against a running deploy yet — smoke-test before
-# relying on it. See issue #24.
+# Smoke-tested end-to-end against a running deploy (issue #24): search via
+# both /v1/vector_stores/{id}/search directly and the file_search tool on a
+# chat completion. Needed several fixes beyond this block to work — a
+# missing api_key here, litellm-pgvector's Prisma schema never having been
+# pushed, a 1536- vs 768-dim mismatch, and its create endpoint ignoring any
+# caller-supplied id — see scripts/update.sh, scripts/ingest-memory.sh, and
+# vendor/litellm-pgvector/'s local patches (models.py, main.py,
+# prisma/schema.prisma).
 vector_store_registry:
   - vector_store_name: memory-and-notes
     litellm_params:
       vector_store_id: "memory-and-notes"
       custom_llm_provider: pg_vector
       api_base: http://litellm-pgvector:8000
+      # Required by litellm's pg_vector provider (see
+      # PGVectorStoreConfig.validate_environment in litellm's source) — it's
+      # the Bearer token litellm-pgvector's own API checks against its
+      # SERVER_API_KEY. Was missing entirely, which is why every vector
+      # store call was failing with "Incorrect API key provided: None"
+      # before litellm-pgvector was ever reached. See issue #24.
+      api_key: os.environ/LITELLM_PGVECTOR_API_KEY
       embedding_model: local-embedding
 
 router_settings: