v1.5.3 — Authenticate MCP connection on self-hosted/Enterprise

Fixed

• MCP server connection now authenticates to self-hosted / Enterprise
  (in-VPC) agents. mcp.json set X-Axonflow-Client and X-License-Token
  static headers but no Authorization header, so against an agent that
  requires HTTP Basic auth the MCP connection arrived unauthenticated → the
  agent 401'd → Cursor fell into OAuth discovery and died on the agent's
  plaintext 404 page not found, and governed tool calls were blocked. Added
  "Authorization": "Basic ${AXONFLOW_AUTH}" to the static headers (Cursor
  expands ${AXONFLOW_AUTH} from the launching environment, same as the
  existing ${AXONFLOW_ENDPOINT} / ${AXONFLOW_LICENSE_TOKEN}). For an
  Enterprise/in-VPC agent set AXONFLOW_AUTH=base64(org_id:license_key) (bare
  base64 — the header adds the Basic prefix). Verified at the wire level:
  the resulting header set returns HTTP 200 + initialize from a live
  in-vpc-enterprise agent. (Distinct from Cursor's lack of a dynamic header
  helper for per-session token refresh; X-License-Token is still forwarded
  statically via env expansion.)