Fix clone button for setups that use different host names for gitlist and git

[steppy]

Summary of Changes

This pull request adds support for configuring custom hostnames (ssh_host and http_host) in config.ini under the [clone_button] section.

It also fixes an issue in Application.php where package.json was loaded with a relative path that broke test execution under certain working directory contexts.

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Motivation / Problem Statement

Previously, the clone button URLs were generated strictly using the current web host (location.hostname).

When GitList is hosted on a separate subdomain/domain (e.g., gitlist.example.com) from the actual Git/SSH remote server (e.g., git.example.com), the generated clone URLs were incorrect (e.g., git@gitlist.example.com:... instead of git@git.example.com:...).

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Changes Introduced

1. Configuration (artifacts/config.ini):

   • Added optional ssh_host (override hostname for SSH clone URLs).
   • Added optional http_host (override hostname for HTTP/HTTPS clone URLs).

2. Backend & Frontend Integration:

   • Passed ssh_host and http_host through the application config to the view/client layer.
   • Updated the clone URL generator (clone-buttons.js) to use the configured hosts when present, falling back to location.hostname if empty.

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Backward Compatibility

• Fully backward compatible: If ssh_host and http_host are left empty (default), GitList falls back to the existing behavior of using the current browser hostname (location.hostname).