This commit replaces the `libvirt` crate with the `virt` crate for managing the libvirt backend on Linux. Key changes include:
- Updated `Cargo.toml` dependencies and feature configuration.
- Refactored hypervisor implementation to align with `virt` crate API.
- Improved error handling and lifecycle management for VMs and networks.
This commit introduces a persistence layer to the Orchestrator, enabling it to optionally connect to a Postgres database for recording job and VM states. It includes:
- SeaORM integration with support for migrations from the migration crate.
- `Persist` module with methods for job and VM state upserts.
- No-op fallback when persistence is disabled or unavailable.
- Documentation updates and test coverage for persistence functionality.
