fix(azure): reuse retail rate cache in pilot admission

[ruby-dlee]

Summary

• route pilot retail-rate admission through the worker provider exact-meter cache owner
• use fresh cached rates without a network call and stale validated rates when the retail API is throttled
• fail closed for absent or malformed cache entries when the live rate is unavailable
• skip the supervisor lookup for the foundation profile, where no supervisor is created

Verification

• bash tests/fm-azure-pilot.test.sh
• bash tests/fm-worker-lifecycle.test.sh
• shellcheck bin/fm-azure-pilot.sh
• python3 -m py_compile bin/fm-azure-worker-provider.py
• git diff --check