data: 13 UK SAT centres have a literal unfilled "lat,lng" placeholder gmaps_link

[yakew7]

Problem

13 records in sat_centre.json (all UK schools, all added_by: Shauryagangrade, same batch as #188/#171) have gmaps_link still set to the literal template placeholder instead of a real link:

"gmaps_link": "https://maps.google.com/?q=lat,lng"

That's the raw <lat>,<lng> placeholder text from the record-shape template, never filled in with the record's own coordinates. lat/lng themselves are correct on these records - it's specifically the gmaps_link field that got left as the template string. This passes npm run validate today because the schema only checks the URL's prefix shape, not that q= is followed by real numbers.

Affected ids: 57137, 57159, 57231, 57295, 57210, 57272, 57630, 57296, 57183, 58351, 60245, 59501, 57216.

Fix

For each of the 13, set gmaps_link to https://maps.google.com/?q=<lat>,<lng> using that record's own already-correct lat/lng (or a real Google Maps place link if you have one handy for that school). While you're in there, scripts/validate-places.mjs could also gain a check that gmaps_link doesn't contain the literal string `lat,lng" - happy to see that added in the same PR so this class of bug can't ship silently again.

Acceptance criteria

• All 13 records have a working gmaps_link that actually points at their coordinates
• (Optional but appreciated) validator catches a literal lat,lng placeholder going forward