fix: reduce stats query limit to 500 to match API max limit

The API endpoint has a max limit of 500 but the stats query was
requesting 1000, causing a 422 validation error.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

static/admin/js/admin-users.js

@@ -208,8 +208,8 @@ function adminUsersPage() {
             adminUsersLog.info('Loading admin user statistics...');
 
             try {
-                // Fetch all admin users to compute stats
-                const url = '/admin/admin-users?skip=0&limit=1000';
+                // Fetch all admin users to compute stats (max 500 per API limit)
+                const url = '/admin/admin-users?skip=0&limit=500';
                 window.LogConfig.logApiCall('GET', url, null, 'request');
 
                 const response = await apiClient.get(url);