feat: add blog index page with posts listing

[alejsdev]

I noticed the Blog link in README.md was broken, and that there was no index page listing the existing posts. I added an index page inspired by the other sections and tried to keep the styling consistent with the rest of the site. I’m opening this PR in case it’s useful. Feel free to adjust, rework, or close it if you prefer a different approach :)

Related Issue: 8731

🎯 What

Add a blog index page at /blog that lists all existing blog posts, fixing the broken link from the README.md.

🤔 Why

The Blog link in README.md was broken because there was no index page, it only had individual post pages. Users clicking the blog link would get a 404 instead of seeing available posts.

🧪 Testing

• I have tested these changes locally
• All existing tests pass (uv run task test for backend, pnpm test for frontend)
• I have run linting and type checking (uv run task lint && uv run task lint_types for backend)

Test Instructions

1. Run pnpm dev
2. Go to http://localhost:3000/blog
3. Verify the blog index page displays the list of posts
4. Click on a post to verify navigation works correctly

🖼️ Screenshots/Recordings

Screencast.from.2025-12-30.15-33-04.mp4

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