Fix Cloud Run invocation ID token

[Pigbibi]

Summary

• generate the Cloud Run invocation token through google-github-actions/auth id_token output
• keep gcloud auth for service URL resolution separate from the invocation token
• update workflow wiring test for the ID token path

Tests

• bash tests/test_invoke_cloud_run_workflow.sh
• /home/ubuntu/Projects/LongBridgePlatform/.venv/bin/python -m ruff check .
• git diff --check