Location-aware reminders

Status summary: deferred. The first implementation was removed from PR #2084 because it committed to an agent event contract, first-phone ownership, MapKit candidate search, and iOS geofencing before the product semantics and background guarantees were convincing. Redesign this independently from the native-build and device-push foundation.

• Define the user-visible reminder lifecycle through real agent conversations: create, confirm, inspect, edit, complete, cancel, repeat, and re-entry behavior.
• Decide who owns a reminder when a project has multiple members and devices; do not silently assign every project reminder to the first phone that sees it.
• Decide whether “near a supermarket” means one confirmed place, a refreshed set of nearby candidates, a category search that moves with the user, or another explicit promise.
• Prototype iOS background behavior across lock, offline, reboot, and force-quit states before selecting the durable contract.
• Specify location privacy, retention, permission degradation, region-budget allocation, travel refresh, and observable failure states.
• Reintroduce native dependencies and server events only after the prototype demonstrates the intended behavior on a physical iPhone.

Prior attempt#

The removed implementation is preserved in branch history through commits beginning at 4ff99799c. It used expo-location, expo-task-manager, a local MKLocalSearch Expo module, /mobile/location-reminders events, and device claim/release reconciliation. Treat it as a prototype to critique, not an API to restore wholesale.