fix(mui): preserve breadcrumb link styling

[RajvardhanVharambale]

Summary

This PR fixes a regression in the @refinedev/mui Breadcrumb component where MUI LinkProps (sx, underline, color, and variant) were forwarded to a native <span> instead of a MUI component.

As a result, these props were rendered as invalid HTML attributes and the intended MUI styling was not applied.

Changes

• Replace the inner <span> in LinkRouter with <MuiLink component="span">
• Preserve the existing router navigation behavior
• Ensure MUI styling props are correctly handled by MuiLink

Result

• ✅ sx styles are applied correctly
• ✅ Hover underline works
• ✅ Color inheritance works
• ✅ Typography variant styling is restored
• ✅ Prevents invalid HTML attributes from being rendered

Validation

• Built @refinedev/mui successfully
• Package declarations generated successfully

Fixes #7462

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Latest commit: ccb3558

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