feat: add CSS file reference for local styled share module

[imyangyong]

Description

When cssCodeSplit is enabled, locally styled shared modules should handle their own CSS imports. Currently, these imports are being omitted in the federated output.

Example:

1. Host configuration (vite.config.ts):

shared: {
   'shared-styled': {}
}

2. Styled shared module source code:

import './style.css'
// module implementation...

3. Current output __federation_shared_shared-styled-{8}.js:

// module code without the CSS import...

Solution:
This PR ensures CSS imports are properly included in the federated output:

import './xxx.css';  // CSS imported
// module code...

Testing
To verify the feature:
pnpm run test:e2e-serve shared-styled

Additional context

---

What is the purpose of this pull request?

• Bug fix
• New Feature
• Documentation update
• Other

Before submitting the PR, please make sure you do the following

• Read the Code of Conduct and follow the Commit Convention guidelines.
• Check that there isn't already a PR that solves the problem the same way to avoid creating a duplicate.
• Provide a description in this PR that addresses what the PR is solving, or reference the issue that it solves (e.g. fixes #123).
• Ideally, include relevant tests that fail without this PR but pass with it.