Fix User listing in admin page

backend/handlers/api_admin.go

@@ -114,14 +114,14 @@ func (app *App) HandleAdminDeleteOrder(w http.ResponseWriter, r *http.Request) {
 }
 
 func (app *App) HandleGetUsers(w http.ResponseWriter, r *http.Request) {
-	rows, err := app.DB.Query("SELECT id, username, role FROM users ORDER BY id")
+	rows, err := app.DB.Query("SELECT id, username, role FROM users WHERE username != 'superadmin' ORDER BY id")
 	if err != nil {
 		http.Error(w, err.Error(), http.StatusInternalServerError)
 		return
 	}
 	defer rows.Close()
 
-	var users []map[string]any
+	users := make([]map[string]any, 0)
 	for rows.Next() {
 		var id, role int
 		var username string