fix: make temp dir if not exist

app.py

@@ -1,3 +1,4 @@
+import os
 import streamlit as st
 from llm import load_llm, response_generator
 from vector_store import load_vector_store, process_pdf
@@ -55,6 +56,9 @@ with st.sidebar:
     if uploaded_files is not None:
         vector_store = load_vector_store()
         for uploaded_file in uploaded_files:
+            temp_dir = "./temp"
+            if not os.path.exists(temp_dir):
+                os.makedirs(temp_dir)
             temp_file = f"./temp/{uploaded_file.name}-{uuid4()}.pdf"
             with open(temp_file, "wb") as file:
                 file.write(uploaded_file.getvalue())