fix: add missing updateUserRole import in admin service

The updateUserRole function was being called but not imported from
auth.service.js, causing "updateUserRole is not defined" error when
changing user roles via admin interface.

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

src/backend/services/admin.service.js

@@ -1,7 +1,7 @@
 import { eq, sql, desc } from 'drizzle-orm';
 import { db, sqlite, logger } from '../config.js';
 import { users, qsos, syncJobs, adminActions, awardProgress, qsoChanges } from '../db/schema/index.js';
-import { getUserByIdFull, isAdmin, isSuperAdmin } from './auth.service.js';
+import { getUserByIdFull, isAdmin, isSuperAdmin, updateUserRole } from './auth.service.js';
 
 /**
  * Log an admin action for audit trail