add empty element per article card, to act as handle for Pinboard 📌 to attach to (using `urlPath` as data attribute)

[twrichards]

Implementation notes

Checklist

General

• [ ] 🤖 Relevant tests added
• [ ] ✅ CI checks / tests run locally
• [ ] 🔍 Checked on CODE

Client

• [ ] 🚫 No obvious console errors on the client (i.e. React dev mode errors)
• [ ] 🎛️ No regressions with existing user interactions (i.e. all existing buttons, inputs etc. work)
• [ ] 📷 Screenshots / GIFs of relevant UI changes included …ndle for pinboard to attach itself (distinguished by the data-url-path attribute)