Exposed API Key in Repository

Description:
While reviewing this repository, I found that an API key has been
hardcoded in the source code / committed to the repository's history,
and is publicly accessible.

Location:
- File: [e.g., backend/.env or config.py]
- Commit hash: [if known]
- Line number: [if applicable]

Key type: [e.g., OpenAI API Key / Anthropic API Key / etc.]

Impact:
If misused, this exposed key could allow unauthorized parties to
consume the key owner's credits/quota, incur unwanted charges, or
gain access to connected services.

Suggested remediation:
1. Revoke/rotate the exposed key immediately.
2. Remove the file from the full git history (not just the latest
commit) using tools like git-filter-repo or BFG Repo-Cleaner.
3. Use environment variables and add the relevant file to
.gitignore to prevent this from happening again.

I'm reporting this privately and responsibly to give you the
opportunity to fix it before it can be exploited.

Thank you for your work on this project.