Email-code sign-in for admins only; Overview with a needs-attention list;
Songs with search, playback, editing, approve/hide and bulk edit; Albums
and Singers with merge; creator applications queue. Adds the admin views,
functions and creator_applications table, a deploy-admin script and a
how-to guide. The admin nginx config no longer caches unhashed JS and
sends its security headers again.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
