use newest langchain package names

rag.py

@@ -1,15 +1,15 @@
-# rag.py  (v3 – imports fixed, no more ModuleNotFoundError)
+# rag.py  (v4 – imports that actually exist today)
 from __future__ import annotations
 import os, uuid, tempfile, requests, shutil, re
 from pathlib import Path
 from functools import lru_cache
 from typing import List, Tuple
 from datasets import load_dataset
-from langchain_text_splitters import RecursiveCharacterTextSplitter
+from langchain.text_splitter import RecursiveCharacterTextSplitter
 from langchain_community.vectorstores import FAISS
 from langchain_huggingface import HuggingFaceEmbeddings, HuggingFaceEndpoint
 from langchain_core.prompts import PromptTemplate
-from langchain.chains.retrieval_qa.base import RetrievalQA  # ← correct path
+from langchain.chains import RetrievalQA
 from supabase import create_client
 
 # ---------- config ----------

requirements.txt

@@ -1,6 +1,5 @@
-# requirements.txt  (no pins = no missing wheels)
 flask
-langchain
+langchain-core
 langchain-community
 langchain-huggingface
 sentence-transformers