feat: check updates using stable repository id

[vitorhugo-dotnet]

Summary

• resolve the GitHub repository from the stable numeric repository ID (1326685411) before requesting the latest release
• avoid hardcoding the current GitHub username/owner in the runtime update flow
• compare the embedded build-N tag with the latest published release
• expose update checks through the Wails desktop bridge
• show an Update build-N action in the desktop header when a newer executable is available
• embed the GitHub Actions run number in the Windows executable through Wails -ldflags

Update flow

1. GET /repositories/1326685411
2. read the repository's current full_name
3. GET /repos/{full_name}/releases/latest
4. compare build-N values
5. surface the .exe asset when a newer build exists

This keeps update discovery working if the account username changes or the repository is transferred/renamed, as long as the repository itself keeps the same numeric ID.

Tests

• backend contract test verifies that repository lookup happens by numeric ID and that the returned renamed owner is used for the release request
• backend test verifies that the current build is not reported as an update
• frontend component tests cover the update action and the no-update state

Notes

Update checks are best-effort and do not block the runner UI if GitHub is unavailable.