Remove Region

Remove a destination from the tracker.

A soft delete (active=False), not a row delete: the region carries immutable published snapshots we must not lose, and OSM/geo identity we'd otherwise have to rebuild if a reader re-requests the same place. Flipping active is enough to remove it everywhere that matters — the public map index, its public report page, and the weekly scan all filter on active — while leaving the history intact and the removal reversible.

Idempotent: removing an already-removed region succeeds without change, so a double click or a stale admin table can't 404 on a region that is, in fact, gone.