Unify LongBridge Cloud Run env management

[Pigbibi]

Summary

• add longbridge-paper to the manual Cloud Run invoke workflow
• collapse Cloud Run env sync into one matrix job for paper/HK/SG
• document the three Environment + trigger setup and runtime target requirements

Verification

• bash tests/test_invoke_cloud_run_workflow.sh
• bash tests/test_sync_cloud_run_env_workflow.sh
• git diff --check