update project dependencies.

requirements.txt

@@ -1,14 +1,16 @@
-fastapi==0.124.4
-uvicorn==0.38.0
-python-multipart==0.0.20
-python-dotenv==1.2.1
-chromadb==0.5.23
-pypdf==6.4.1
-sentence-transformers==5.2.0
-aiofiles==24.1.0
-langchain
-langchain-groq
-langchain-huggingface
-langchain-chroma
-langchain-community
-langchain-experimental
+fastapi==0.112.0
+uvicorn==0.30.0
+python-multipart==0.0.9
+python-dotenv==1.0.1
+aiofiles==23.2.1
+pypdf==4.3.1
+sentence-transformers==3.0.1
+chromadb==0.5.5
+
+# --- LangChain Stable Stack (v0.2) ---
+langchain==0.2.14
+langchain-community==0.2.12
+langchain-core==0.2.33
+langchain-groq==0.1.9
+langchain-huggingface==0.0.3
+langchain-chroma==0.1.3