build(deps): bump langchain from 1.2.7 to 1.3.9

Bumps [langchain](https://github.com/langchain-ai/langchain) from 1.2.7 to 1.3.9.
- [Release notes](https://github.com/langchain-ai/langchain/releases)
- [Commits](langchain-ai/langchain@langchain==1.2.7...langchain==1.3.9)

---
updated-dependencies:
- dependency-name: langchain
  dependency-version: 1.3.9
  dependency-type: direct:production
...

Signed-off-by: dependabot[bot] <support@github.com>

Author: dependabot[bot]

pyproject.toml

@@ -8,7 +8,7 @@ requires-python = ">=3.10,<3.14"
 [project.optional-dependencies]
 dev = [
     "nbformat>=5.10.4",
-    "langchain>=0.3.21",
+    "langchain>=1.3.9",
     "pinecone>=6.0.2",
     "python-dotenv>=1.0.1",
     "tiktoken>=0.9.0",