feat(figma): add BannerAlert Code Connect and fix ButtonIcon node URL

[georgewrmarshall]

Description

Adds Figma Code Connect files for BannerAlert in both React and React Native, and fixes a stale Figma node URL in ButtonIcon for both platforms.

BannerAlert (9315-372)

• New BannerAlert.figma.tsx for React and React Native
• Maps severity enum (Info / Success / Warning / Danger) — Figma's "Neutral" variant falls through to the component default
• Maps title and description string props
• Intentionally omits Figma-only properties: has Art, has Title, is Dismissible, has Action

ButtonIcon (5226-5609, was 1:2860)

• Updates stale node URL to current Figma component
• Fixes prop name mismatches: 'isDisabled' → 'disabled', 'variant' → 'state' to match actual Figma property names

Related issues

Fixes:

Manual testing steps

1. Open the BannerAlert Figma component in Dev Mode
2. Verify the React and React Native code snippets appear in the Code Connect panel with correct severity/title/description props
3. Open the ButtonIcon Figma component in Dev Mode
4. Verify the code snippet reflects the correct size/isDisabled/variant props

Screenshots/Recordings

Before

• ButtonIcon pointed to stale node 1:2860 (unmapped in Figma)
• BannerAlert had no Code Connect files

After

• ButtonIcon connected to 5226-5609 with correct prop mappings
• BannerAlert connected to 9315-372 for both React and React Native

Pre-merge author checklist

• I've followed MetaMask Contributor Docs
• 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.

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