feat: pre-registrant management and invitation system

Admin interface to review, filter, and batch-invite the 95 pre-registrants
from Baby Ghosts. Accept-invitation page pre-fills their data and collects
circle, pronouns, motivation, contribution tier, and agreement before
creating their member record.

tests/server/api/admin-auth-guards.test.js

@@ -31,6 +31,14 @@ const adminRoutes = {
     'series/[id].delete.js',
     'series/[id].put.js',
     'series/tickets.put.js'
+  ],
+  'admin/pre-registrants/': [
+    'pre-registrants/index.get.js',
+    'pre-registrants/[id].get.js',
+    'pre-registrants/[id].put.js',
+    'pre-registrants/bulk-status.patch.js',
+    'pre-registrants/invite.post.js',
+    'pre-registrants/stats.get.js'
   ]
 }
 
@@ -50,7 +58,11 @@ const businessLogicPatterns = [
   'Event.countDocuments',
   'Series.find',
   'Series.findOne',
-  'Series.findById'
+  'Series.findById',
+  'PreRegistration.find',
+  'PreRegistration.findById',
+  'PreRegistration.aggregate',
+  'PreRegistration.updateMany'
 ]
 
 describe('Admin endpoint auth guards', () => {