feat(auth): make upload review a separate grant instead of an admin privilege

Reviewing the upload queue is now a per-user flag (reviews_uploads), not part
of the admin role: several people can hold it, a moderator can have it, and an
admin may not. Only admins grant or revoke it; existing admins keep it.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

packages/core/src/auth.test.ts

@@ -11,6 +11,7 @@ const user = {
   ui_prefs: {},
   must_change_password: false,
   must_change_credentials: false,
+  reviews_uploads: false,
   created_at: '2026-01-01T00:00:00Z',
 };