add migration code

modules/migration_server.py

@@ -0,0 +1,17 @@
+import git
+from aiohttp import web
+from server import PromptServer
+
+manager_core_path = None
+manager_core_url = "https://github.com/Comfy-Org/manager-core"
+
+@PromptServer.instance.routes.get("/manager/install_manager_core")
+def install_manager_core(request):
+    if manager_core_path is not None:
+        repo = git.Repo.clone_from(manager_core_url, manager_core_path)
+        repo.git.clear_cache()
+        repo.close()
+    else:
+        print(f"[ComfyUI Manager] Failed to install `manager-core`")
+
+    return web.Response(status=200)