Add CodeFlash GitHub Actions workflow

[codeflash-ai]

This PR adds the CodeFlash GitHub Actions workflow to automatically find optimizations for new code in future pull requests.

The workflow will:

• Run on every pull request when Python code is modified
• Automatically attempt to optimize Python code
• Create optimization suggestions when improvements are found

Setup Required:

To use this workflow, you'll need to add the CODEFLASH_API_KEY secret to your repository:

1. Get your API key from codeflash.ai
2. Go to your repository settings: Settings → Secrets and variables → Actions
3. Click New repository secret
4. Name: CODEFLASH_API_KEY
5. Value: Your CodeFlash API key
6. Click Add secret

The workflow will use this key to authenticate with CodeFlash's optimization service.