host api alignment (#7)

* feat: add Firecracker API client methods for VM pause/resume and snapshots

Add PatchVm, GetVm, PutSnapshotCreate, and PutSnapshotLoad methods to the
API client, along with supporting types (VmState, SnapshotCreateParams,
SnapshotLoadParams, MemBackend).

* feat: add snapshot data layer - contract types, model, store, config

Add SnapshotID and snapshot contract types, SnapshotRecord model,
store interface CRUD methods with file store implementation,
snapshot paths helper, SnapshotsDir config, and directory creation.

* feat: add runtime methods for VM pause, resume, snapshot, and restore

Implement Pause, Resume, CreateSnapshot, and RestoreBoot on the
firecracker Runtime. RestoreBoot launches a jailer, stages snapshot
files into the chroot, loads the snapshot, and resumes the VM.

* feat: add daemon snapshot create, restore, and reconciliation logic

Implement CreateSnapshot (pause, snapshot, COW-copy disk, resume),
RestoreSnapshot (COW-copy disk, RestoreBoot, wait for guest),
GetSnapshot, ListSnapshots, DeleteSnapshotByID, and crash recovery
reconciliation for snapshot and restore operations.

* feat: add HTTP endpoints for snapshot create, get, list, delete, restore

Wire 5 snapshot routes: POST /machines/{id}/snapshots (create),
GET /machines/{id}/snapshots (list), GET /snapshots/{id} (get),
DELETE /snapshots/{id} (delete), POST /snapshots/{id}/restore (restore).

* fix: cross-device rename, restore network, and snapshot cleanup

- Replace os.Rename with copy+remove for moving snapshot files out of
  /proc/<pid>/root/ (cross-device link error on Linux)
- Reconfigure network interface after snapshot load so the restored VM
  uses its own tap device instead of the source VM's
- Clean partial snapshot dirs immediately on failure instead of only
  via reconcile
- Reject snapshot requests while a machine operation is already pending

* fix: test and modify snapshot runtime

* feat: snapshot lifecycle update, align runtime issues between host image
and daemon

internal/firecracker/state.go

@@ -5,6 +5,27 @@ import "time"
 // Phase represents the lifecycle phase of a local microVM.
 type Phase string
 
+// SnapshotPaths holds the file paths for a VM snapshot.
+type SnapshotPaths struct {
+	MemFilePath   string
+	StateFilePath string
+}
+
+// SnapshotLoadSpec describes what is needed to restore a VM from a snapshot.
+type SnapshotLoadSpec struct {
+	ID              MachineID
+	SnapshotPath    string
+	MemFilePath     string
+	DiskPaths       map[string]string // drive ID -> host path
+	RootFSPath      string
+	KernelImagePath string
+	VCPUs           int64
+	MemoryMiB       int64
+	KernelArgs      string
+	Vsock           *VsockSpec
+	Network         *NetworkAllocation
+}
+
 // MachineState describes the current host local state for a machine.
 type MachineState struct {
 	ID          MachineID