The admin and marketing site sit outside the compose stack, so `make app`
never started them. Add `make admin` and `make site` to launch each
workspace's dev server (Vite on 5174, Astro on 4321), and update the root
README and admin/README to point at them instead of the old "open
localhost:5174" line that implied `make app` was enough.
Also add `make grant-admin EMAIL=... [ROLE=super|support|ops|analyst]`
plus `make revoke-admin` so the first super-admin can be seeded without
hand-writing SQL. Role bitmasks mirror AdminRolePermissions in
internal/models/admin_permission.go.
