Decouple Performance Page from Brand Plugin and Add Standalone Tools Integration

[arunshenoy99]

Proposed changes

This PR moves the Performance page from the Brand Plugin App Nav to its own standalone page under the Tools menu in the WordPress admin.

This requires thorough testing because:

1. We now use our own Tailwind and PostCSS setup along with the Newfold UI library, and no longer rely on the plugin’s styling pipeline.
2. We have implemented dynamic brand support using CSS variables, allowing the page to adapt its appearance based on the active brand without depending on the plugin. (We will eventually need to move branding to a common location. I'll discuss this with the plugins team. For now, this serves as a reference implementation. I also have a few ideas on how we can standardize this across modules.)
3. We’ve created a custom Redux store specifically for the performance module, removing any dependency on the plugin’s store.
4. We use separate Webpack configurations for building both the general-purpose JS assets and the React SPA, replacing the plugin’s build system.
5. This is a completely standalone implementation. We no longer rely on any plugin components, methods, or utilities in any way.

Note: This needs to go out after #135

Type of Change

Production

• Bugfix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Dependency update
• Refactoring / housekeeping (changes to files not directly related to functionality)

Development

• Tests
• Dependency update
• Environment update / refactoring
• Documentation Update

Video

Checklist

• I have read the CONTRIBUTING doc
• I have viewed my change in a web-browser
• Linting and tests pass locally with my changes
• I have added tests that prove my fix is effective or that my feature works
• I have added necessary documentation (if appropriate)

Further comments