fix: embedding URL path missing /v1 prefix

The embedding endpoint path was  but OpenAI-compatible APIs
serve embeddings at . When EMBEDDING_BASE_URL is set to a
bare host (e.g. https://llm.aviron.ai), the resulting URL would be
/eembeddings instead of /v1/embeddings, returning 404.

Changed defaultBaseURL to not include /v1 and always use /v1/embeddings
as the endpoint path.

.env.example

@@ -3,7 +3,7 @@ QDRANT_PORT=6334
 # QDRANT_API_KEY=
 # QDRANT_TLS=false
 OPENAI_API_KEY=sk-...
-# EMBEDDING_BASE_URL=https://api.openai.com/v1
+# EMBEDDING_BASE_URL=https://api.openai.com
 EMBEDDING_MODEL=text-embedding-3-small
 MCP_TOKEN=change-me
 PORT=8080