Implement GitHub data caching mechanism

[neubig]

This PR implements a caching mechanism for GitHub data to improve performance and security:

• Creates a cache script that fetches and stores GitHub data in a JSON file
• Modifies the GitHub service to read from cache instead of making direct API calls
• Updates build process to include cache generation
• Changes environment variable from VITE_GITHUB_TOKEN to GITHUB_TOKEN (no longer exposed to frontend)

Benefits:

• GitHub token is no longer exposed to the frontend
• Reduced API calls to GitHub (only when building or manually updating cache)
• Faster frontend performance since it reads from a local file
• Maintains all existing functionality including date filtering

[vercel]

@openhands-agent is attempting to deploy a commit to the all-hands-ai team on Vercel, but is not a member of this team. To resolve this issue, you can:

• Make your repository public. Collaboration is free for open source and public repositories.
• Add @openhands-agent as a member. A Pro subscription is required to access Vercel's collaborative features.
  • If you're the owner of the team, click here and add @openhands-agent as a member.
  • If you're the user who initiated this build request, click here to request access.
  • If you're already a member of the all-hands-ai team, make sure that your Vercel account is connected to your GitHub account.

To read more about collaboration on Vercel, click here.