Fix langchain dependency conflicts

- Update langchain to 0.1.20 for compatibility
- Update langchain-community to 0.0.38
- Update langchain-openai to 0.1.8
- Update langchain-core to 0.1.52
- Resolve ResolutionImpossible error with compatible versions

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <[email protected]>

requirements.txt

@@ -6,10 +6,10 @@ numpy==1.24.3
 openpyxl==3.1.2
 
 # Fixed Langchain components
-langchain==0.1.0
-langchain-community==0.0.10
-langchain-openai==0.0.5
-langchain-core==0.1.10
+langchain==0.1.20
+langchain-community==0.0.38
+langchain-openai==0.1.8
+langchain-core==0.1.52
 sentence-transformers==2.2.2
 faiss-cpu==1.7.4
 transformers==4.36.0