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>

Models/Facility.cs

@@ -21,25 +21,30 @@ namespace Fitness_core_BE.Models
         [MaxLength(128)]
         public string Name { get; set; } = string.Empty;
 
-        /// <summary>"Scheduled" | "AdHoc". Scheduled: staff pre-creates fixed-time
-        /// FacilitySessions that many bookings share one capacity pool against (classes).
-        /// AdHoc: a booking claims one of NumberOfUnits identical units directly for an
-        /// arbitrary time window, no pre-created session needed (courts/pool).</summary>
-        public string BookingMode { get; set; } = "Scheduled";
+        /// <summary>Staff pre-creates fixed-time FacilitySessions (classes) that many bookings
+        /// share one capacity pool against. Independent of SupportsBooking -- both can be true,
+        /// e.g. a court that hosts a scheduled class AND accepts ad-hoc walk-in bookings outside
+        /// class hours.</summary>
+        public bool SupportsClasses { get; set; } = true;
+
+        /// <summary>A booking can claim one of NumberOfUnits identical units directly for an
+        /// arbitrary time window, no pre-created session needed (courts/pool). At least one of
+        /// SupportsClasses/SupportsBooking must be true.</summary>
+        public bool SupportsBooking { get; set; } = false;
 
         [MaxLength(500)]
         public string? Description { get; set; }
 
-        /// <summary>Default per-session headcount limit when BookingMode == "Scheduled"; a
-        /// specific FacilitySession can override.</summary>
+        /// <summary>Default per-session headcount limit when SupportsClasses; a specific
+        /// FacilitySession can override.</summary>
         public int DefaultCapacity { get; set; } = 1;
 
-        /// <summary>Number of identical, independently-bookable units when BookingMode ==
-        /// "AdHoc" (e.g. 3 for "3 courts") -- availability is this minus overlapping
-        /// non-cancelled/non-completed AdHoc bookings in the requested window.</summary>
+        /// <summary>Number of identical, independently-bookable units when SupportsBooking (e.g.
+        /// 3 for "3 courts") -- availability is this minus overlapping non-cancelled/
+        /// non-completed WalkIn bookings in the requested window.</summary>
         public int NumberOfUnits { get; set; } = 1;
 
-        /// <summary>Hourly rate used to compute a guest AdHoc booking's suggested AmountCharged
+        /// <summary>Hourly rate used to compute a guest WalkIn booking's suggested AmountCharged
         /// (PricePerHour * duration-in-hours) at creation time.</summary>
         public decimal PricePerHour { get; set; } = 0m;