* fix: respect server's token endpoint auth methods for MCP OAuth refresh
Previously, LibreChat always used Basic Auth when refreshing OAuth tokens if a
client_secret was present. This caused issues with servers (like FastMCP) that
only support client_secret_post. Now properly checks and respects the server's
advertised token_endpoint_auth_methods_supported.
Fixes token refresh failures with error: "refresh_token.client_id: Field required"
* chore: remove MCP OAuth URL Logging
