- Add Zone model (id, tenantId, name, description, isActive)
- Add ZoneAssignment model (collector-to-zone join table)
- Replace Subscriber.zone String? with Subscriber.zoneId FK to Zone
- Add Zone + ZoneAssignment to TENANT_SCOPED_MODELS with full operation blocks
- Add "Zone" to AppSubjects in types.ts
- Grant OFFICE_STAFF manage Zone, COLLECTOR read Zone in permissions.ts
- Migration 20260305000000_add_zones applied to DB
