Refactor HTML Edit.jsx: Class Component to Functional Component

[Manik-Khajuria-5]

Issue number

Contributes to #4460

Description

This PR refactors the HTML Block Edit.jsx component by modernizing it into a fully hook-based functional component.

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Key Changes

• Converted the HTML block Edit.jsx into a functional component using React hooks
• Replaced legacy lifecycle patterns with useEffect, useRef, and useCallback
• Improved code editor selection and focus restoration logic
• Simplified state management for preview and source modes
• Improved overall readability and consistency with modern Volto code style

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