fix(a11y): add aria-label to dashboard IconButton and unlabeled call sites

Icon-only buttons (delete, row settings, column settings) had no
accessible name, making them invisible to screen readers despite being
keyboard-focusable via tabIndex=0. Wires the existing label prop through
as aria-label on the underlying div[role=button] and provides labels at
all three call sites that previously passed none.

WCAG 2.1 SC 4.1.2 (Name, Role, Value) — Level A.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

superset-frontend/src/dashboard/components/DeleteComponentButton.tsx

@@ -18,6 +18,7 @@
  */
 import { MouseEventHandler, FC } from 'react';
 
+import { t } from '@apache-superset/core/translation';
 import { Icons } from '@superset-ui/core/components/Icons';
 import type { IconType } from '@superset-ui/core/components/Icons/types';
 import IconButton from './IconButton';
@@ -33,6 +34,7 @@ const DeleteComponentButton: FC<DeleteComponentButtonProps> = ({
 }) => (
   <IconButton
     onClick={onDelete}
+    label={t('Delete component')}
     icon={<Icons.DeleteOutlined iconSize={iconSize ?? 'l'} />}
   />
 );

superset-frontend/src/dashboard/components/IconButton.tsx

@@ -43,6 +43,7 @@ const IconButton = ({ icon, label, onClick }: IconButtonProps) => (
   <StyledDiv
     tabIndex={0}
     role="button"
+    aria-label={label}
     onClick={e => {
       e.preventDefault();
       onClick(e);

superset-frontend/src/dashboard/components/gridComponents/Column/Column.tsx

@@ -247,6 +247,7 @@ const Column = (props: ColumnProps) => {
               />
               <IconButton
                 onClick={() => handleChangeFocus(true)}
+                label={t('Column settings')}
                 icon={<Icons.SettingOutlined iconSize="m" />}
               />
             </HoverMenu>

superset-frontend/src/dashboard/components/gridComponents/Row/Row.tsx

@@ -293,6 +293,7 @@ const Row = memo((props: RowProps) => {
             <DeleteComponentButton onDelete={handleDeleteComponent} />
             <IconButton
               onClick={() => handleChangeFocus(true)}
+              label={t('Row settings')}
               icon={<Icons.SettingOutlined iconSize="l" />}
             />
           </HoverMenu>