feat: implement openai-compatible fallback for cloud mode

[memreo]

Summary

This PR implements an OpenAI-compatible failover fallback for the GenAI py-intelligence service. If the primary cloud model (Gemini) fails during analysis, the system catches the exception and falls back to querying the custom "Logos" API gateway. The base API URL and key are configurable via environment variables (OPENAI_BASE_URL and OPENAI_API_KEY), which have been added to the project's local .env and Github Actions secrets.

Component

• Client: client/
• API contract: api/
• Spring ingestion: services/spring-ingestion/
• Spring logbook: services/spring-logbook/
• Spring alerts: services/spring-alerts/
• GenAI: services/py-intelligence/
• Infrastructure: infra/
• CI/CD: .github/workflows/
• Documentation

API Impact

• This changes the API.
• api/openapi.yaml was updated.
• This does not change the API.

Testing

• I tested this locally.
• I added or updated tests.
• Tests are not applicable for this change.

Checklist

• Branch name follows (feat|fix)/(issue_id)/(name_of_issue).
• The change is limited to the intended component(s).
• Documentation was updated if needed.

Related Issue

Closes #