Use trigger tokens for portal GitLab submits

[yoshifuminakamura]

Summary

• switch Portal GitLab submits from the Create Pipeline API to the Pipeline Trigger API
• use RESULT_SERVER_GITLAB_TRIGGER_TOKEN env names for default and named targets
• render trigger-style dry-run payloads and keep trigger tokens out of stored request records

Validation

• /home/nakamura/fugakunext/venv/bin/python -m py_compile result_server/utils/gitlab_pipeline.py result_server/routes/admin.py
• /home/nakamura/fugakunext/venv/bin/python -m pytest result_server/tests/test_execution_profiles.py
• /home/nakamura/fugakunext/venv/bin/python -m pytest result_server/tests/test_execution_profiles.py result_server/tests/test_app_dev_security.py result_server/tests/test_api_routes.py result_server/tests/test_preflight.py