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/api_test.go

@@ -0,0 +1,54 @@
+package firecracker
+
+import (
+	"context"
+	"io"
+	"net/http"
+	"testing"
+)
+
+func TestPutSnapshotLoadIncludesNetworkOverrides(t *testing.T) {
+	var (
+		gotPath string
+		gotBody string
+	)
+
+	socketPath, shutdown := startUnixSocketServer(t, func(w http.ResponseWriter, r *http.Request) {
+		body, err := io.ReadAll(r.Body)
+		if err != nil {
+			t.Fatalf("read request body: %v", err)
+		}
+		gotPath = r.URL.Path
+		gotBody = string(body)
+		w.WriteHeader(http.StatusNoContent)
+	})
+	defer shutdown()
+
+	client := newAPIClient(socketPath)
+	err := client.PutSnapshotLoad(context.Background(), SnapshotLoadParams{
+		SnapshotPath: "vmstate.bin",
+		MemBackend: &MemBackend{
+			BackendType: "File",
+			BackendPath: "memory.bin",
+		},
+		ResumeVm: false,
+		NetworkOverrides: []NetworkOverride{
+			{
+				IfaceID:     "net0",
+				HostDevName: "fctap7",
+			},
+		},
+	})
+	if err != nil {
+		t.Fatalf("put snapshot load: %v", err)
+	}
+
+	if gotPath != "/snapshot/load" {
+		t.Fatalf("request path mismatch: got %q want %q", gotPath, "/snapshot/load")
+	}
+
+	want := "{\"snapshot_path\":\"vmstate.bin\",\"mem_backend\":{\"backend_type\":\"File\",\"backend_path\":\"memory.bin\"},\"resume_vm\":false,\"network_overrides\":[{\"iface_id\":\"net0\",\"host_dev_name\":\"fctap7\"}]}"
+	if gotBody != want {
+		t.Fatalf("request body mismatch:\n got: %s\nwant: %s", gotBody, want)
+	}
+}