fix: Add langchain-classic>=0.1.0 dependency

Added langchain-classic as explicit dependency to fix import errors
on Streamlit Cloud deployment.

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

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

Author: 2 people

pyproject.toml

@@ -11,6 +11,7 @@ authors = [
 
 dependencies = [
     "langchain>=1.0.0",
+    "langchain-classic>=0.1.0",
     "langchain-openai>=0.1.22",
     "langchain-mistralai>=0.1.12",
     "langchain_community>=0.2.9",