fix(vexa-bot): detect Google Meet admission denial

[vikas-writer]

Summary

• Detect Google Meet host-denial states before treating the bot as still in the waiting room.
• Add denial/retry UI selectors and map admission rejection to a failed lifecycle with awaiting_admission_rejected metadata.
• Include lifecycle reason metadata in status pub/sub payloads so consumers can distinguish admission denial from generic failures.

Test plan

• npx --yes --package tsx tsx src/platforms/googlemeet/admission.test.ts
• python3 -m py_compile services/meeting-api/meeting_api/callbacks.py
• Rebuilt local vexa-bot and meeting-api images and verified services healthy locally.

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