Fix build: replace nonexistent pyaudioop with audioop-lts; drop unused legacy langchain import

app.py

@@ -1,6 +1,5 @@
 import openai
 import gradio as gr
-from langchain import LLMChain, OpenAI, PromptTemplate
 from langchain_openai import ChatOpenAI
 from langchain_core.prompts import ChatPromptTemplate
 from langchain_core.output_parsers import StrOutputParser

requirements.txt

@@ -1,6 +1,4 @@
 openai
-langchain
-gradio
-langchain_community
-langchain_openai
-pyaudioop
+langchain-openai
+langchain-core
+audioop-lts; python_version >= "3.13"