Embeds a Model Context Protocol (MCP) server into the Memos HTTP
process, exposing memo operations as MCP tools at POST/GET /mcp using
Streamable HTTP transport.

Authentication is PAT-only — requests without a valid personal access
token receive HTTP 401. Six tools are exposed: list_memos, get_memo,
create_memo, update_memo, delete_memo, and search_memos, all scoped to the authenticated user.