Implement plugin settings page using DataForm

[proweb]

This commit refactors the admin dashboard to use the @wordpress/dataviews
package, specifically the DataForm component, as described in the
WordPress Developer Blog article.

Key changes:

• Added @wordpress/dataviews and other missing @WordPress dependencies.
• Registered 'dashboard_demo_settings' in PHP with a structured schema.
• Created 'useSettings' custom hook for handling settings state via REST API.
• Refactored 'src/index.js' to use a configuration-driven DataForm.
• Fixed CSS linting issues in 'style.css'.
• Updated build artifacts.

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PR created automatically by Jules for task 12750035017575129359 started by @proweb

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