Update openai requirement from >=1.0.0 to >=2.43.0

Updates the requirements on [openai](https://github.com/openai/openai-python) to permit the latest version.
- [Release notes](https://github.com/openai/openai-python/releases)
- [Changelog](https://github.com/openai/openai-python/blob/main/CHANGELOG.md)
- [Commits](openai/openai-python@v1.0.0...v2.43.0)

---
updated-dependencies:
- dependency-name: openai
  dependency-version: 2.43.0
  dependency-type: direct:production
...

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

Author: dependabot[bot]

requirements.txt

@@ -1,5 +1,5 @@
 # Core evolution system
-openai>=1.0.0          # LLM client (OpenAI-compatible: Mistral, Ollama, etc.)
+openai>=2.43.0          # LLM client (OpenAI-compatible: Mistral, Ollama, etc.)
 pytest>=7.0.0          # Test execution for generated code
 flake8>=6.0.0          # Linting for generated code