build: make langchain-serve optional

src/backend/langflow/__main__.py

@@ -80,7 +80,7 @@ def jcloud():
     import click
 
     try:
-        from lcserve.__main__ import serve_on_jcloud
+        from lcserve.__main__ import serve_on_jcloud  # type: ignore
     except ImportError:
         click.secho(
             "🚨 Please install langchain-serve to deploy Langflow server on Jina AI Cloud using `pip install langchain-serve`",

src/backend/langflow/lcserve.py

@@ -11,4 +11,4 @@ app.mount(
     "/",
     StaticFiles(directory=static_files_dir, html=True),
     name="static",
-)
+)