build(deps): update langchain-openai requirement from 0.3.27 to 0.3.28

Updates the requirements on [langchain-openai](https://github.com/langchain-ai/langchain) to permit the latest version.
- [Release notes](https://github.com/langchain-ai/langchain/releases)
- [Commits](langchain-ai/langchain@langchain-openai==0.3.27...langchain-openai==0.3.28)

---
updated-dependencies:
- dependency-name: langchain-openai
  dependency-version: 0.3.28
  dependency-type: direct:production
...

Signed-off-by: dependabot[bot] <[email protected]>

Author: dependabot[bot]

pyproject.toml

@@ -28,7 +28,7 @@ beautifulsoup4 = "4.13.4"
 jieba = "0.42.1"
 
 # LLM及AI相关
-langchain-openai = "0.3.27"
+langchain-openai = "0.3.28"
 langchain-anthropic = "0.3.17"
 langchain-community = "0.3.27"
 langchain-deepseek = "0.1.3"