Add traffic splitting automation

**Summary**: Implement automated traffic splitting that gradually routes traffic from old revisions to new revisions based on configuration.

**Acceptance Criteria**:
- [ ] Configurable traffic percentage routing between revisions
- [ ] Automated traffic shifting based on health checks and success metrics
- [ ] Traffic split validation and monitoring
- [ ] Dynamic traffic adjustment during deployment
- [ ] Traffic routing rollback on failure detection
- [ ] Integration with Container Apps traffic management features