Set a verified MCP server's public owner response

Publishes a plain-text owner response (≤500 chars; control and bidi/zero-width characters are stripped server-side) rendered on the public MCP-readiness report. Verified claims only (409 otherwise). An empty note clears it. The {id} path parameter is the URL-encoded server endpoint URL. Authorization: the update is scoped in SQL to the caller's own organization's verified claim for this server (owner_org_id = <caller's org>); a server the caller has not verified for their own org matches no row and returns 409, so another org's claim is never visible or mutable.