fix: avoid hardcoded main branch redirect when no refs exist

[Ontiomacer]

Proposed change

Resolves l3montree-dev/devguard #1472
l3montree-dev/devguard#1472

This PR fixes a frontend redirect issue where clicking a repository assumed a
main branch exists and redirected to /refs/main, causing a 500 error when
no default branch or refs are present.

Summary of changes

• Removed hardcoded main branch fallback
• Redirects now resolve in the following order:
  • repository.defaultBranch (if available)
  • first available branch
  • first available tag
• If no refs exist, redirect is skipped entirely
• Prevents invalid /refs/main URLs from being constructed

Testing

• Reproduced the issue locally
• Verified redirect logic no longer assumes a default branch
• Full end-to-end auth testing is limited locally due to Kratos requirements

[Ontiomacer]

Hi @Hubtrick-Git ,

I’ve opened a pull request in the devguard-web repository implementing the discussed fix.
The redirect logic now resolves refs in a safe order and skips redirecting entirely if none are available, preventing the 500 error.

Please let me know if any adjustments are needed.