Fix/pages lowercase redirect loop

fixes #526293

This MR fixes a redirect loop issue in GitLab Pages when accessing lowercase URLs for projects with mixed-case slugs, specifically when "Use unique domain" is disabled.

Modified the GitLab Pages configuration logic to provide an additional "lookup path" with a lowercased prefix whenever a project slug contains mixed-case characters.

• Updated Pages::LookupPath to support prefix overrides.
• Updated Pages::VirtualDomain to generate a secondary lowercase lookup path for mixed-case project slugs.

This ensures that bit-for-bit, both the original case and the lowercase variant of the URL correctly route to the project's Pages deployment.