fix: removing circular dependencies from avatar favicon

[georgewrmarshall]

Description

This PR continues the work to remove circular dependencies by addressing the re-export of AvatarBaseSize as AvatarFaviconSize. Instead of re-exporting AvatarBaseSize, we now define a dedicated AvatarFaviconSize enum in the AvatarFavicon.types.ts file. This change:

1. Removes the circular dependency between AvatarFavicon and AvatarBase
2. Makes the AvatarFavicon component more self-contained
3. Improves maintainability by explicitly defining size values for AvatarFavicon

This is part of a larger effort to clean up circular dependencies in the design system.

Related issues

Partially fixes: #445

Manual testing steps

1. Run storybook and verify all AvatarFavicon stories render correctly
2. Run tests and ensure all tests pass
3. Check build process completes successfully

Screenshots/Recordings

Before

N/A (No visual changes)

After

N/A (No visual changes)

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Pre-merge reviewer checklist

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