Add Revision REST API endpoints

## Overview

Implement REST API endpoints for DeploymentRevision management.

## Tasks

1. Create REST endpoints:
- POST /deployments/{id}/revisions - Create new revision
- GET /deployments/{id}/revisions - List revisions
- GET /deployments/{id}/revisions/{revision_number} - Get revision detail
- POST /deployments/{id}/revisions/{revision_number}/promote - Promote revision
- POST /deployments/{id}/rollback - Rollback to previous revision
1. Implement request validation using DTOs
1. Implement proper error responses
1. Add OpenAPI documentation
1. Write integration tests

## Notes

- Promote/rollback should update deployment_state and traffic_status accordingly

JIRA Issue: BA-3432