* New 'locations' table for reusable venues (Tractor Supply, Boot Barn,
etc.) — each stop now links via stops.location_id while keeping the
denormalized location text for backwards compat.
* 6 SECURITY DEFINER RPCs: admin_create_location, admin_create_locations_batch,
admin_update_location, admin_delete_location, admin_attach_location_to_stop,
get_locations_for_brand. Plus admin_list_locations for the admin tab.
* Backfill: 26 unique venues extracted from the 269 Tuxedo stops, all linked.
* Stops & Routes page now has tabs (Stops | Locations) via ?tab= query param.
Locations tab has full CRUD UI: search, status filter, pagination, edit,
delete, add-venue modal.
* StopsHeaderActions now tab-aware — Upload Schedule / Add Stop only show on
Stops tab; Locations tab has its own Add Venue button inline.
