Cleaned up old Attendees model. Updated tests.

frontend/src/db.js

@@ -40,6 +40,12 @@ db.version(3).stores({
   outbox: '++id, table, op, synced_at',
 })
 
+db.version(4).stores({
+  attendees: null,
+  outbox: null,
+  volunteers: 'id, name, department_id, checked_in, participant_id, deleted_at',
+})
+
 export async function getLastSync() {
   const m = await db.meta.get('last_sync')
   return m?.value ?? ''