Addresses the actual root cause behind the Denmark 2026 corrupted-coordinate
bug: there was no supported way to set an entry's location to somewhere other
than the current GPS position, forcing hand-typed/pasted raw coordinates
through Admin2's fragile text field. Backend sanitization (cache-on-save)
already guards against silent corruption; this spec adds a frontend way to
avoid needing that path at all.
m038
2ab6575e4b