feat: Add storage management for VM creation and resizing

- Introduced storage parameter in VmCreateRequest and VmResizeRequest models.
- Implemented storage validation to ensure minimum and maximum limits.
- Enhanced CLI to support storage options during VM creation and resizing.
- Updated lifecycle management to handle pending resize operations for VM resources.
- Added methods for resizing VM disks and validating storage capacity.
- Updated API endpoints to accommodate new storage functionality.
- Refactored related validation and configuration logic to support storage management.

USAGE.md

@@ -44,7 +44,7 @@ You need:
 - KVM enabled and readable/writable at `/dev/kvm`.
 - Linux >= 5.3 with native bridge conntrack and safe pidfd support.
 - Root access for installation and VM lifecycle operations.
-- An x86_64 host for the default guest kernel/rootfs downloads.
+- An x86_64 or ARM64 (`aarch64`) host, including NVIDIA DGX Spark.
 - Internet access if downloading Firecracker and guest assets.
 - `iproute2`, `iptables`, `nftables`, `conntrack`, `e2fsprogs`, `util-linux`,
   `openssl`, and `openssh-client`; `install` installs the host packages.
@@ -140,6 +140,23 @@ UVM installs host packages, Firecracker, Jailer, a guest kernel, and a guest
 rootfs template. It requires SHA-256 checksums by default because it downloads
 artifacts that will be used by a privileged process.
 
+### ARM64 Hosts (NVIDIA DGX Spark)
+
+UVM detects the host architecture and selects matching Firecracker, kernel,
+and rootfs downloads. NVIDIA DGX Spark uses the `aarch64` assets; the `arm64`
+architecture alias is also accepted. The default ARM64 guest downloads are:
+
+- Kernel: `https://s3.amazonaws.com/spec.ccfc.min/img/quickstart_guide/aarch64/kernels/vmlinux.bin`
+- Rootfs: `https://s3.amazonaws.com/spec.ccfc.min/img/quickstart_guide/aarch64/rootfs/bionic.rootfs.ext4`
+
+Use the installation commands below with checksums for those ARM64 artifacts
+and the ARM64 Firecracker release archive. `UVM_KERNEL_URL` and
+`UVM_ROOTFS_URL` can override either download independently. Custom images must
+match the host architecture and the [guest image contract](README.md#guest-image-contract).
+On ARM64, the kernel must be an uncompressed ARM64 Linux `Image` (PE format),
+and the rootfs must be an ARM64 ext4 filesystem. UVM adds `keep_bootcon` to the
+guest boot arguments for ARM64 console output.
+
 ### Scenario: Strict First Installation
 
 Obtain trusted checksums independently, then run:
@@ -196,8 +213,7 @@ sudo env UVM_ALLOW_UNVERIFIED_DOWNLOADS=1 ./uvm.py start VM
 | `/dev/kvm does not exist` | Enable hardware/nested virtualization first. |
 | `checksum is required` | Provide the requested `UVM_*_SHA256` variable. |
 | `SHA-256 mismatch` | Stop and obtain the correct digest or artifact URL. |
-| `unsupported host architecture` | Use x86_64 defaults or provide compatible assets. |
-| `default guest assets support x86_64 only` | Configure both custom kernel and rootfs URLs for ARM. |
+| `unsupported host architecture` | Use an x86_64 or ARM64 Linux host. |
 
 ## 5. Create VMs
 
@@ -306,6 +322,12 @@ On failure, UVM attempts containment and cleanup. It does not release the
 disk or IP reservation if safe process exit or cleanup cannot be confirmed;
 inspect the retained `failed` record and `last_error` before retrying.
 
+After updating UVM to fix a create/cleanup error, restart the API server to
+load the updated code. To discard a failed creation and release its reserved
+IP, run `sudo ./uvm.py delete VM -y` with that failed VM's exact ID, or send
+an authenticated `DELETE /vms/VM`. Deletion retries the outstanding cleanup
+and removes the failed VM's private disk. Then retry the create request.
+
 ## 6. Inspect VMs
 
 ```sh
@@ -938,8 +960,8 @@ automatically detects every conflict with host routes or other managers.
 | `UVM_NETWORK` | Guest subnet; default `10.42.0.0/24` |
 | `UVM_GATEWAY` | Guest gateway / bridge IP; default `10.42.0.1` |
 | `UVM_BRIDGE` | Linux bridge name; default `uvm0` |
-| `UVM_KERNEL_URL` | Custom kernel download URL |
-| `UVM_ROOTFS_URL` | Custom rootfs download URL |
+| `UVM_KERNEL_URL` | Override the host-architecture default kernel URL |
+| `UVM_ROOTFS_URL` | Override the host-architecture default rootfs URL |
 | `UVM_FIRECRACKER_SHA256` | Strict Firecracker archive checksum |
 | `UVM_KERNEL_SHA256` | Strict kernel checksum |
 | `UVM_ROOTFS_SHA256` | Strict rootfs checksum |