Add canvas JSON import export

src/app/api/canvas/projects/import/route.ts

@@ -0,0 +1,18 @@
+import { NextResponse } from "next/server";
+import { importCanvasProjectExport } from "@/lib/server/services/canvas-project-transfer";
+
+export const runtime = "nodejs";
+
+export async function POST(request: Request) {
+  const payload = await request.json().catch(() => null);
+
+  try {
+    const project = importCanvasProjectExport(payload);
+    return NextResponse.json({ item: project }, { status: 201 });
+  } catch (err) {
+    return NextResponse.json(
+      { error: err instanceof Error ? err.message : "导入画布失败" },
+      { status: 400 },
+    );
+  }
+}