Facility booking-mode redesign, multi-plan subscriptions, and Classes

Implements the facility-classes-booking-dashboard plan (backend):

- Facility.BookingMode (single Scheduled/AdHoc choice) replaced with
  independent SupportsClasses/SupportsBooking flags, so one facility
  can run a class and accept walk-in bookings; a running class now
  blocks walk-in booking for its window on both create and reschedule.
- CustomerPlan.GrantsGymAccess + CustomerPlanClass join table let a
  customer hold one gym-access plan plus any number of class-only
  plans. Replaced the old single-subscription resolution
  (GetActiveSubscriptionByCustomerId/HasAnyActiveSubscriptionAsync)
  with gym-access-aware and class-aware resolvers across booking
  creation/cancellation, plan assignment, and customer self-service.
  Fixed ChangeMembershipPlan/renewal plan-changes, which resolved "the
  subscription to replace" by most-recent-created and would have
  deactivated a member's class subscription instead of their gym one.
- New FacilityClass model: recurring class definitions (Daily/Weekly/
  Monthly/Custom) with lazy occurrence generation (8-week horizon,
  race-safe via a unique index) and proper unlimited-capacity handling.
  "Mark not held" replaces the old bare-cancel: cascades to cancel and
  refund every confirmed booking on the occurrence through the same
  core CancelBooking uses, and frees the slot for walk-in booking.
  Scheduling conflicts (a walk-in booking now overlapping a class) are
  surfaced for staff to resolve via the existing Reschedule flow.
- Renamed the pre-existing "AdHoc" booking-mode terminology to
  "WalkIn" throughout (routes, methods, DTOs, the stored BookingMode
  value) for a clearer, simpler name.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

Interfaces/IFacilityRepository.cs

@@ -12,9 +12,14 @@ namespace Fitness_core_BE.Interfaces
 
         Task<FacilitySession> CreateFacilitySession(FacilitySession session);
         Task<FacilitySession?> GetFacilitySessionById(Guid facilitySessionId);
-        Task<List<FacilitySession>> GetSessions(Guid clientId, Guid? facilityId, DateTime fromUtc, DateTime toUtc);
+        Task<List<FacilitySession>> GetSessions(Guid clientId, Guid? facilityId, DateTime fromUtc, DateTime toUtc, bool includeCancelled = false);
         Task<int> GetActiveBookingCount(Guid facilitySessionId);
-        Task<FacilitySession?> CancelFacilitySession(Guid facilitySessionId, Guid clientId);
+        Task<List<FacilitySession>> GetOverlappingActiveSessionsAsync(Guid facilityId, DateTime startUtc, DateTime endUtc);
+
+        /// <summary>"Mark not held" -- see FacilityService.CancelFacilitySession for the full
+        /// cascade this backs. Returns the session with its Bookings included so the caller can
+        /// cancel+refund each Confirmed one.</summary>
+        Task<FacilitySession?> MarkFacilitySessionNotHeldAsync(Guid facilitySessionId, Guid clientId, string? reason);
 
         // Device binding (absorbed from the old IPlaceRepo -- one AccessDevice per Facility).
         Task<AccessDevice?> GetDeviceByIdForClientAsync(Guid deviceId, Guid clientId);
@@ -30,15 +35,15 @@ namespace Fitness_core_BE.Interfaces
         Task<Dictionary<Guid, List<Guid>>> GetFacilityIdsByPlanIdsAsync(List<Guid> customerPlanIds);
         Task<Dictionary<Guid, string>> GetFacilityNamesByIdsAsync(List<Guid> facilityIds);
 
-        // AdHoc booking support (new). See TenantDbContext's Booking (FKFacilityId, StartTime,
+        // WalkIn booking support (new). See TenantDbContext's Booking (FKFacilityId, StartTime,
         // EndTime) index comment -- overlap is checked here rather than by a DB constraint.
-        /// <summary>Counts non-cancelled/non-completed AdHoc bookings on this facility whose
+        /// <summary>Counts non-cancelled/non-completed WalkIn bookings on this facility whose
         /// [StartTime, EndTime) overlaps the given window. Pass excludeBookingId when
         /// re-checking a booking being rescheduled, so it doesn't count against itself.</summary>
-        Task<int> GetOverlappingAdhocBookingCountAsync(Guid facilityId, DateTime startTime, DateTime endTime, Guid? excludeBookingId = null);
+        Task<int> GetOverlappingWalkInBookingCountAsync(Guid facilityId, DateTime startTime, DateTime endTime, Guid? excludeBookingId = null);
 
         /// <summary>Issues a row lock on the facility (SELECT ... FOR UPDATE) inside the caller's
-        /// already-open unit-of-work transaction, serializing concurrent AdHoc-slot claims on the
+        /// already-open unit-of-work transaction, serializing concurrent WalkIn-slot claims on the
         /// same facility so two overlapping bookings can't both pass the overlap-count check.</summary>
         Task LockFacilityForUpdateAsync(Guid facilityId);
     }