Camera packs keep their nearest cameras and the catalog cap thins them
further, so London answered 250 cameras while TfL offers many more. The
catalog now records each pack's full count, tags cameras with their pack,
and serves the packs it trimmed; find_cctv_cameras names them.
Supersedes #438 by @rileygramlich, ported onto the current component layout with fixes from review.
Verified before merge: format, package boundaries, unit suite, build, and the browser tracking suite; a browser harness for the change where one applies; adversarial review applied.
Co-authored-by: rileygramlich <[email protected]>