Replace decommissioned Vercel app with GitHub API for repository cards

[Copilot]

The repositories page depends on github-readme-stats.vercel.app which is no longer operational, breaking repository card rendering.

Changes

Replaced Vercel service with client-side GitHub API calls

• Created _includes/repository/repo_card.html template that fetches repository metadata via fetch() from GitHub's public API
• Renders cards with description, stars, forks, and language with appropriate styling
• Added CSS grid layout and hover effects in _sass/_base.scss

Error handling and optimization

• Validates HTTP responses before parsing to handle rate limits and 404s
• Shares language color map across instances to reduce memory overhead
• Falls back to error message on API failures

fetch(`https://api.github.com/repos/${repo}`)
  .then(response => {
    if (!response.ok) {
      throw new Error(`GitHub API error: ${response.status}`);
    }
    return response.json();
  })
  .then(data => {
    // Update card with live data
  })

No external dependencies required—uses standard Fetch API and GitHub's unauthenticated public endpoints (60 req/hr sufficient for 2 repos).

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