Create or reconcile this directory's own widget on Cloudflare

Gives the directory a Turnstile widget of its own, registered against the domain recorded on it plus that domain's www alias, and stores both halves. Normally nobody calls this by hand — setting domain on a directory does it — so this route is for the two cases that need a nudge: a directory that already had a domain before provisioning existed, and one whose Cloudflare hostname list was edited in the dashboard and has drifted from what we last sent. It always re-sends the hostname list rather than trusting our own record of it.

Idempotent, and it refuses to touch a widget registered by hand: those come back skipped-manual and no request is made to Cloudflare. A directory with no domain comes back skipped-no-domain — there is no hostname to register.