fix(a11y): add role=alert to form error messages

frontend/src/components/settings/ChangePasswordForm.tsx

@@ -195,7 +195,7 @@ export function ChangePasswordForm() {
       )}
 
       {error && (
-        <div className="rounded-md bg-error/10 border border-error/30 px-3 py-2">
+        <div className="rounded-md bg-error/10 border border-error/30 px-3 py-2" role="alert">
           <p className="text-xs text-error">{error}</p>
         </div>
       )}

frontend/src/components/users/CreateUserForm.tsx

@@ -120,7 +120,7 @@ export function CreateUserForm({ tenantId, open, onClose }: Props) {
               </SelectContent>
             </Select>
           </div>
-          {error && <p className="text-xs text-error">{error}</p>}
+          {error && <p className="text-xs text-error" role="alert">{error}</p>}
           <DialogFooter>
             <Button type="button" variant="ghost" onClick={handleClose} size="sm">
               Cancel