feat: add helm charts and cleanup
- Added Helm charts for deploying AI2
- Renamed OpenOP_BACKEND_OAI and OpenOP_Backend → OEG_SERVICE_URL across Helm, Docker Compose and Python code
- Removed MCP_HOST, APP_HOST env vars from Helm and Docker Compose
- Added readinessProbe / livenessProbe to MCP and an initContainer to ai-agent so it waits for MCP to be healthy before starting
- Fixed Docker Compose: Python-based healthcheck (no curl in slim image), service_healthy condition on depends_on, removed deprecated version field
- Updated READMEs to reflect all of the above