chore(deps): bump langchain from 0.3.25 to 0.3.26

Bumps [langchain](https://github.com/langchain-ai/langchain) from 0.3.25 to 0.3.26.
- [Release notes](https://github.com/langchain-ai/langchain/releases)
- [Commits](langchain-ai/langchain@langchain==0.3.25...langchain==0.3.26)

---
updated-dependencies:
- dependency-name: langchain
  dependency-version: 0.3.26
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

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

Author: dependabot[bot]

requirements/base.txt

@@ -1,6 +1,6 @@
 
 isort==6.0.1
-langchain==0.3.25
+langchain==0.3.26
 langchain-community==0.3.21
 langchain-core==0.3.65
 langchain-experimental==0.3.4