Accessibility fix pass for twenty-ui input components (#21776)

Re-enables the live Storybook axe gate across the twenty-ui `input`
domain (17 story files) by removing the inherited `a11y: { test: 'todo'
}` overrides. Pilot for the wider a11y fix pass; other domains follow
the same playbook.

**What changed**
- Accessible names added to icon-only buttons, `Toggle`, `Checkbox`, and
the button groups via small additive `aria-label`/`ariaLabel` props on 8
components. Where this fully fixes the story, the override is dropped so
the full gate applies.
- Color-contrast (design-token level) is deferred — not changed — via a
new shared `A11Y_DEFER_COLOR_CONTRAST` parameter (`@ui/testing`) that
disables only the `color-contrast` rule while every other axe rule stays
enforced. Grep the constant to find all deferrals when tokens are
darkened later.
- `CatalogDecorator`: unique cell ids (clears `duplicate-id-aria`) and
dimension titles switched from empty `h1/h2/h3` to `div` (clears
`empty-heading`). Both help every domain's catalogs.

**Reviewer notes**
- No visual change: edits are aria / id / story-args / axe-config only,
so Argos parity holds.
- Input axe gate goes from 12 failing to 60/60 passing; typecheck and
lint green.

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packages/twenty-ui/src/input/ButtonGroup/__stories__/ButtonGroup.stories.tsx

@@ -1,6 +1,7 @@
 import { type Meta, type StoryObj } from '@storybook/react-vite';
 import { IconCheckbox, IconNotes, IconTimelineEvent } from '@ui/icon';
 import {
+  A11Y_DEFER_COLOR_CONTRAST,
   CatalogDecorator,
   type CatalogStory,
   ComponentDecorator,
@@ -22,8 +23,7 @@ export default meta;
 type Story = StoryObj<typeof ButtonGroup>;
 
 export const Default: Story = {
-  // TODO(a11y): violations inherited from deprecated story; fix during a11y pass
-  parameters: { a11y: { test: 'todo' } },
+  parameters: { a11y: A11Y_DEFER_COLOR_CONTRAST },
   args: {
     size: 'small',
     variant: 'primary',
@@ -55,8 +55,7 @@ export const Catalog: CatalogStory<Story, typeof ButtonGroup> = {
     children: { control: false },
   },
   parameters: {
-    // TODO(a11y): violations inherited from deprecated story; fix during a11y pass
-    a11y: { test: 'todo' },
+    a11y: A11Y_DEFER_COLOR_CONTRAST,
     pseudo: { hover: ['.hover'], active: ['.pressed'], focus: ['.focus'] },
     catalog: {
       dimensions: [