Harden direct Dokploy rollback break-glass

[cbusillo]

Summary

• fail closed when manual direct Dokploy rollback is dispatched without a rollback image or reason
• pass the operator reason into the emergency rollback script
• include the operator reason in reviewable break-glass evidence

Tests

• git diff --check
• uv run --extra dev ruff check scripts/deploy/emergency-dokploy-rollback.py tests/test_emergency_dokploy_rollback.py tests/test_product_onboarding.py --diff
• uv run --extra dev ruff check scripts/deploy/emergency-dokploy-rollback.py tests/test_emergency_dokploy_rollback.py tests/test_product_onboarding.py
• uv run python -m unittest tests.test_emergency_dokploy_rollback tests.test_product_onboarding
• docker run --rm -v "$PWD:/repo" -w /repo rhysd/actionlint:1.7.7 -config-file .github/actionlint.yaml .github/workflows/deploy-launchplane.yml

Refs #1049