Add GET/PUT /api/groups/:groupId/routes endpoints that filter and merge
routes by group (backend forces groupId from the path param). Rework the
console so the top level lists groups; entering a group shows and manages
only that group's routes. Drop the route-level group selector and the
now-redundant group badge on route cards.
Add a super-admin-only Groups tab to create, edit and delete groups
(name, admin ids, owner scope). Routes now require a group via a select
in the editor, group names are shown on route cards, and the new
useMe/useGroups composables back the UI.
Add an admin WebUI (Nuxt static SPA in admin/, served via the ASSETS
binding) for managing routes and viewing send logs. Access is gated by
GitHub OAuth plus an ADMIN_USER_IDS whitelist with cookie sessions
(admin-session.ts). Expose routes/logs CRUD API (admin-routes.ts), add a
discord-link mapping in token-store.ts, and mount admin routes with an
SPA assets fallback in the server.
