Add CLI commands for scale unit management

**Summary**: Implement CLI commands that allow users to manage scale units, including deployment, status checking, and operational tasks.

**Acceptance Criteria**:
- [ ] `azd provision scale-unit ` command implementation
- [ ] `azd down scale-unit ` for scale unit teardown
- [ ] `azd infra show scale-units` to list all scale units
- [ ] Cross-region status aggregation and reporting
- [ ] Scale unit-specific logging and diagnostics