Add required status checks to branch protection ruleset

[jeremyeder]

Context

Extracted from #605 (now closed). Branch protection rulesets are in place with PR requirements, squash-only merges, and force-push/deletion blocking.

Missing: required status checks before merging. Currently a PR can be merged even if CI is failing.

Proposed Change

Add required_status_checks rule to the repo-level protect-main ruleset requiring key CI workflows to pass:

• go-lint (backend + operator)
• frontend-lint
• components-build-deploy

This can be done in Settings > Rules > protect-main or via API.

References

• Closed issue: Enable branch protection on default branch #605
• Repo ruleset: https://github.com/ambient-code/platform/rules/13424890