fix: change AlertSnackbar variant from 'filled' to 'outlined'

src/components/ui/AlertSnackbar.tsx

@@ -7,7 +7,7 @@ const Alert = React.forwardRef<HTMLDivElement, AlertProps>(function Alert(
   props,
   ref,
 ) {
-  return <MuiAlert elevation={6} ref={ref} variant="filled" {...props} />;
+  return <MuiAlert elevation={6} ref={ref} variant="outlined" {...props} />;
 });
 
 export interface AlertSnackbarProps {