fixes to app.py

app.py

@@ -151,8 +151,8 @@ async def upload_file(file: UploadFile = File(...)):
     index.add(embeddings)
 
     SESSION_DATA[session_id] = {
-        "chunks": text_chunks,
-        "index": index.serialize(), # Store the index as bytes
+        "filename": file.filename,
+        "index": faiss.write_index_buf(index), # Store the index as bytes
     }
     
     logger.info(f"Session {session_id} created with {len(text_chunks)} chunks.")