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/store/store.go

@@ -27,4 +27,8 @@ type Store interface {
 	UpsertOperation(context.Context, model.OperationRecord) error
 	ListOperations(context.Context) ([]model.OperationRecord, error)
 	DeleteOperation(context.Context, contracthost.MachineID) error
+	CreateSnapshot(context.Context, model.SnapshotRecord) error
+	GetSnapshot(context.Context, contracthost.SnapshotID) (*model.SnapshotRecord, error)
+	ListSnapshotsByMachine(context.Context, contracthost.MachineID) ([]model.SnapshotRecord, error)
+	DeleteSnapshot(context.Context, contracthost.SnapshotID) error
 }