style: update the focus outline in the menu item component

[matteoscurati]

Description

This PR updates the outline style when the user navigates menu items using the TAB key. This ensures the user can clearly identify which item is currently focused.

Related issues

#26728

Manual testing steps

1. Open the menu
2. Navigate through the items using the TAB key
3. Verify that the outline is displayed correctly on the focused item

Screenshots/Recordings

Before

After

https://www.loom.com/share/25a3748a1a8b49e6b3cf617ccf791240?sid=cbe7a8d6-46d9-431a-a0dd-682c6cf209a2

Pre-merge author checklist

• I've followed MetaMask Contributor Docs and MetaMask Extension Coding Standards.
• I've completed the PR template to the best of my ability
• I’ve included tests if applicable
• I’ve documented my code using JSDoc format if applicable
• I’ve applied the right labels on the PR (see labeling guidelines). Not required for external contributors.

Pre-merge reviewer checklist

• I've manually tested the PR (e.g. pull and build branch, run the app, test code being changed).
• I confirm that this PR addresses all acceptance criteria described in the ticket it closes and includes the necessary testing evidence such as recordings and or screenshots.

[github-actions]

CLA Signature Action: All authors have signed the CLA. You may need to manually re-run the blocking PR check if it doesn't pass in a few minutes.

[metamaskbot]

Builds ready [7fdc4f0]

• builds: chrome, firefox
• builds (flask): chrome, firefox
• builds (MMI): chrome
• builds (test): chrome, firefox
• builds (test-flask): chrome, firefox
• build viz: Build System
• mv3: Bundle Size Stats
• mv2: E2e Actions Stats
• storybook: Storybook
• typescript migration: Dashboard
• all artifacts
• bundle viz:

  • background: 0, 1, 2, 3, 4, 5, 6, 7
  • common: 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13
  • ui: 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13
  • content-script: 0
  • offscreen: 0

Page Load Metrics (1715 ± 67 ms)

Platform	Page	Metric	Min (ms)	Max (ms)	Average (ms)	StandardDeviation (ms)	MarginOfError (ms)
Chrome	Home	firstPaint	285	1984	1566	422	203
		domContentLoaded	1457	2035	1690	143	69
		load	1512	2046	1715	140	67
		domInteractive	26	141	56	32	15
		backgroundConnect	5	85	28	22	11
		firstReactRender	16	101	53	31	15
		getState	4	95	14	21	10
		initialActions	0	1	0	0	0
		loadScripts	1040	1591	1255	129	62
		setupStore	6	76	17	22	10
		uiStartup	1676	2487	2058	239	115

Bundle size diffs [🚀 Bundle size reduced!]

• background: -3 Bytes (-0.00%)
• ui: -1 Bytes (-0.00%)
• common: -1 Bytes (-0.00%)