test(smoke): decouple admin checks from bootstrap credentials

[XiaoSeS]

Closes #626.

Summary

• Decouple smoke-test admin label checks from bootstrap admin credentials.
• Add explicit SMOKE_ADMIN_USERNAME/SMOKE_ADMIN_PASSWORD inputs and SMOKE_ADMIN_CHECKS mode.
• Add script regression coverage and document persistent-environment usage.

Scope

• scripts/smoke-test.sh admin mode behavior
• Makefile staging smoke credentials
• PR Scripts regression workflow
• README and dev workflow docs

Verification

• bash scripts/tests/smoke-test-admin-mode-test.sh
• bash scripts/tests/workflow-security-test.sh
• git diff --check HEAD~1 HEAD
• Local exact-SHA release Compose preview passed smoke test.
• GitHub PR checks passed.