Convert homepage workshops section to use a Jekyll collection

[mmcky]

Summary

The homepage "Recent Workshops" section in _layouts/home.html is currently hardcoded HTML. Each time a new workshop is added to pages/workshops.md, the homepage list must be manually updated separately.

Proposal

Convert workshops to a Jekyll collection (similar to _lectures/ and _projects/) so the homepage can dynamically render the most recent workshops using a Liquid loop.

This would:

• Eliminate the need to update two places when adding a workshop
• Keep the homepage automatically in sync with the workshops page
• Make it easier to maintain workshop data (each workshop as a separate YAML/markdown file)

Current behaviour

• Homepage workshops list: hardcoded in _layouts/home.html (lines ~144-180)
• Full workshops page: hardcoded in pages/workshops.md
• Adding a workshop requires editing both files manually