fix: race condition allows auto-verify/auto-merge on AI-resolved cherry-pick PRs

[myakove]

Problem

When a cherry-pick PR is created with AI-resolved conflicts, the ai-resolved-conflicts label is added AFTER PR creation via add_to_labels. This creates a race condition:

1. gh pr create creates the PR on GitHub
2. GitHub immediately fires pull_request.opened webhook
3. Webhook handler checks for ai-resolved-conflicts label — label doesn't exist yet
4. Auto-verify and auto-merge proceed because the label is missing
5. Only after does the cherry-pick handler add the label via PyGithub

Additionally, set_pull_request_automerge() has NO check for ai-resolved-conflicts label at all.

Expected Behavior

Cherry-pick PRs with AI-resolved conflicts should NOT be auto-verified or auto-merged, since they require manual review.

Observed Behavior

PR #350 in RedHatQE/mtv-api-tests was auto-verified and auto-merged despite having AI-resolved conflicts.

Deliverables

• Add --label flags to gh pr create command for cherry-pick PRs so labels are present from creation
• Add ai-resolved-conflicts check in set_pull_request_automerge()
• Add tests for the race condition fix