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>

Repos/CustomerSubscriptionRepository.cs

@@ -134,23 +134,69 @@ namespace Fitness_core_BE.Repos
                 .ToListAsync();
         }
 
-        public async Task<CustomerSubscription?> GetActiveSubscriptionByCustomerId(Guid customerId)
+        // A plan with no CustomerPlanClass links is an ordinary gym plan -- GrantsGymAccess is
+        // never consulted for it (always true in effect). A class-linked plan only grants gym
+        // access when GrantsGymAccess is explicitly set. Reused by every gym-access query below.
+        private IQueryable<CustomerPlan> GymAccessPlans() => _context.CustomerPlans.Where(p =>
+            !_context.CustomerPlanClasses.Any(c => c.FKCustomerPlanId == p.CustomerPlanId) || p.GrantsGymAccess);
+
+        public Task<bool> PlanGrantsGymAccessAsync(Guid customerPlanId, CancellationToken ct = default)
+            => GymAccessPlans().AnyAsync(p => p.CustomerPlanId == customerPlanId, ct);
+
+        public async Task<CustomerSubscription?> GetActiveGymAccessSubscriptionAsync(Guid customerId)
         {
             return await _context.CustomerSubscriptions
                 .Include(s => s.TenantCustomerLink)
                 .Include(s => s.CustomerPlan)
                 .Where(s => s.FKCustomerId == customerId && s.IsActive)
+                .Where(s => GymAccessPlans().Any(p => p.CustomerPlanId == s.FKCustomerPlanId))
                 .OrderByDescending(s => s.CreatedAt)
                 .FirstOrDefaultAsync();
         }
 
+        public async Task<CustomerSubscription?> GetActiveSubscriptionForPlanAsync(Guid customerId, Guid customerPlanId)
+        {
+            return await _context.CustomerSubscriptions
+                .Include(s => s.CustomerPlan)
+                .Where(s => s.FKCustomerId == customerId && s.IsActive && s.FKCustomerPlanId == customerPlanId)
+                .OrderByDescending(s => s.CreatedAt)
+                .FirstOrDefaultAsync();
+        }
+
+        /// <summary>Resolves which of the customer's (possibly several) active subscriptions
+        /// covers a specific class, preferring one that still has quota left this cycle over one
+        /// that's already exhausted it -- two different plans can link the same class.</summary>
+        public async Task<CustomerSubscription?> GetActiveSubscriptionForClassAsync(Guid customerId, Guid facilityClassId)
+        {
+            var candidates = await _context.CustomerSubscriptions
+                .Include(s => s.CustomerPlan)
+                .Where(s => s.FKCustomerId == customerId && s.IsActive)
+                .Where(s => _context.CustomerPlanClasses.Any(c =>
+                    c.FKCustomerPlanId == s.FKCustomerPlanId && c.FKFacilityClassId == facilityClassId))
+                .OrderByDescending(s => s.CreatedAt)
+                .ToListAsync();
+
+            bool HasQuota(CustomerSubscription s)
+            {
+                if (!s.CustomerPlan.SessionsPerCycle.HasValue) return true;
+                var carriedOver = s.SessionsCarriedOverExpiresAt.HasValue && s.SessionsCarriedOverExpiresAt.Value < DateTime.UtcNow
+                    ? 0 : s.SessionsCarriedOver;
+                return s.SessionsUsedThisCycle < s.CustomerPlan.SessionsPerCycle.Value + carriedOver;
+            }
+
+            return candidates.FirstOrDefault(HasQuota) ?? candidates.FirstOrDefault();
+        }
+
         // SubscriptionMembers always has a row for the primary too (CustomerSubscriptionFactory
         // adds it alongside the CustomerSubscription itself), so this one query covers both
-        // "primary somewhere" and "secondary/group member somewhere" in a single check.
-        public Task<bool> HasAnyActiveSubscriptionAsync(Guid customerId, CancellationToken ct = default)
+        // "primary somewhere" and "secondary/group member somewhere" in a single check. Scoped
+        // to gym-access plans only -- a class-only subscription never blocks a second one via
+        // this check (unlimited concurrent class-only subscriptions are allowed).
+        public Task<bool> HasActiveGymAccessPlanAsync(Guid customerId, CancellationToken ct = default)
         {
             return _context.SubscriptionMembers.AnyAsync(m =>
-                m.FKCustomerId == customerId && m.IsActive && m.Subscription.IsActive, ct);
+                m.FKCustomerId == customerId && m.IsActive && m.Subscription.IsActive &&
+                GymAccessPlans().Any(p => p.CustomerPlanId == m.Subscription.FKCustomerPlanId), ct);
         }
 
         // ---------- Group membership ----------