The store dashboard

≈ 6 min100 pts max

Context

The back office shows a "Latest orders" widget on the tablet of every store (≈ 800 stores), refreshed every 10 seconds.

This PR adds the endpoint behind it. CI is green, and the local demo (seed database: 3 orders) is instant. It ships to production tomorrow morning.

Find the line that will hurt the database in production, then name the problem.