Adds a GET /monitors/domain/:monitorId endpoint that looks up the
registrable domain's WHOIS expiry date (walking up from subdomains),
and displays it next to the certificate expiry on the uptime details
page.
Fixes#2094
Adapted from #3579 by @gorkem-bwl. The openapi/registry, helpers, and
per-resource routes/* files are largely their work; this commit relocates
the directory out of src/ so the build-time generator code is not emitted
into dist/, and shifts spec generation from runtime to a build step.
Co-authored-by: gorkem-bwl <gorkem.cetin@bluewavelabs.ca>