[Bug] Links open Github.com instead of Github Enterprise

### Short summary

Links to repositories hosted on GitHub Enterprise (GHE) incorrectly open on GitHub.com instead of the configured GitHub Enterprise instance.

### Affected version or release

v1.0.23

### Installation context

_No response_

### What happened?

When viewing a project that is hosted on a GitHub Enterprise (GHE) server, the application's "Open in GitHub" link generates a URL pointing to github.com rather than the configured GitHub Enterprise domain.
As a result, users are redirected to GitHub.com, where the repository does not exist, instead of being taken to the correct repository location in their enterprise environment.

### Steps to reproduce

1. Open Settings.
2. Select a project hosted on a GitHub Enterprise (GHE) instance.
3. Locate and click the Open in GitHub link.
4. Observe that the browser opens a URL on github.com instead of the configured GitHub Enterprise server.
5. The resulting page either returns a 404 error or points to an incorrect repository location.

### Expected behavior

The Open in GitHub link should use the repository's configured GitHub Enterprise base URL and open the repository on the correct GHE instance.

For example:
- Actual: https://github.com/company/project
- Expected: https:///company/project

### Actual behavior

The application always constructs links using the GitHub.com domain, even when the selected project is hosted on GitHub Enterprise.
Impact

Users are unable to navigate directly to repositories hosted on GitHub Enterprise.
Repository links result in broken pages or incorrect destinations.
Creates confusion for organisations that exclusively use GitHub Enterprise.

### Additional context

The issue appears to affect projects configured to use GitHub Enterprise and may indicate that the repository host URL is not being read from the project configuration when generating external repository links.

Start in the Settings flow where a project is selected and the "Open in GitHub" link is generated. Reproduce with a project hosted on GitHub Enterprise and trace how the repository URL is formed; done means the link uses the project's configured enterprise base URL rather than github.com and opens the correct repository.

索引モデルが issue の本文から書いたものです。