feat: Enhance booking functionality with invoice management and dashboard summary

- Added customerId to guest booking requests for better identification.
- Implemented new endpoints for managing booking invoices and dashboard summaries.
- Created BookingInvoice and BookingDashboardSummary DTOs to support new features.
- Updated Booking and BookingInvoice models to include payment method and timestamps.
- Enhanced BookingService to handle invoice creation upon payment confirmation.
- Modified BookingRepository to support CRUD operations for BookingInvoice.
- Updated TenantDbContext to include BookingInvoice DbSet and relevant configurations.
- Improved error handling and validation for booking completion and payment processes.

DTOs/Booking/BookingDashboardSummaryDto.cs

@@ -0,0 +1,12 @@
+namespace Fitness_core_BE.DTOs.Booking
+{
+    /// <summary>Backs the Bookings page's Dashboard tab stat-card row.</summary>
+    public class BookingDashboardSummaryDto
+    {
+        public int BookingsToday { get; set; }
+        public decimal RevenueToday { get; set; }
+        public int CheckedInNow { get; set; }
+        public int UpcomingConfirmed { get; set; }
+        public decimal OutstandingUnpaid { get; set; }
+    }
+}

DTOs/Booking/BookingDto.cs

@@ -37,6 +37,9 @@ namespace Fitness_core_BE.DTOs.Booking
 
         public string PaymentStatus { get; set; } = string.Empty;
         public decimal AmountCharged { get; set; }
+        /// <summary>"Cash" | "Bank". Null until PaymentStatus becomes "Paid".</summary>
+        public string? PaymentMethod { get; set; }
+        public DateTime? PaidAt { get; set; }
         public string Status { get; set; } = string.Empty;
         public DateTime BookedAt { get; set; }
         public DateTime? CheckedInAt { get; set; }

DTOs/Booking/BookingInvoiceDto.cs

@@ -0,0 +1,21 @@
+namespace Fitness_core_BE.DTOs.Booking
+{
+    /// <summary>A booking payment receipt -- deliberately separate from the membership-based
+    /// CustomerInvoice, listed on its own "Invoices" tab, not mixed into Customer Payments.</summary>
+    public class BookingInvoiceDto
+    {
+        public Guid BookingInvoiceId { get; set; }
+        public Guid BookingId { get; set; }
+        public decimal Amount { get; set; }
+        public string PaymentMethod { get; set; } = string.Empty;
+        public string GuestName { get; set; } = string.Empty;
+        public string? GuestPhone { get; set; }
+        public string FacilityName { get; set; } = string.Empty;
+        public DateTime BookingStartTime { get; set; }
+        public DateTime BookingEndTime { get; set; }
+        public DateTime IssuedAt { get; set; }
+
+        /// <summary>Public, unauthenticated link to this receipt's printable page.</summary>
+        public string? ShareUrl { get; set; }
+    }
+}

DTOs/Booking/BookingRequests.cs

@@ -18,6 +18,11 @@ namespace Fitness_core_BE.DTOs.Booking
 
         [Required]
         public string GuestPhone { get; set; } = string.Empty;
+
+        /// <summary>Optional link to an existing registered customer (TenantCustomerLinkId) when
+        /// staff recognizes the walk-in as an already-registered member -- purely for
+        /// identification/auto-fill, doesn't change payment/membership handling at all.</summary>
+        public Guid? CustomerId { get; set; }
     }
 
     public class CreateAdhocBookingRequest
@@ -57,6 +62,10 @@ namespace Fitness_core_BE.DTOs.Booking
         /// the FE pre-fills this from the facility but lets staff adjust it.</summary>
         [Range(typeof(decimal), "0", "79228162514264337593543950335", ErrorMessage = "PricePerHour cannot be negative")]
         public decimal? PricePerHour { get; set; }
+
+        /// <summary>Optional link to an existing registered customer -- see
+        /// CreateGuestBookingRequest.CustomerId.</summary>
+        public Guid? CustomerId { get; set; }
     }
 
     public class MarkGuestBookingPaidRequest
@@ -67,6 +76,20 @@ namespace Fitness_core_BE.DTOs.Booking
         [Required]
         [Range(0.01, double.MaxValue, ErrorMessage = "AmountCharged must be greater than zero")]
         public decimal AmountCharged { get; set; }
+
+        /// <summary>"Cash" | "Bank". Defaults to "Cash" if omitted.</summary>
+        public string? PaymentMethod { get; set; }
+    }
+
+    /// <summary>Body for POST .../complete. Only required when the booking is a guest booking
+    /// still Unpaid -- see BookingService.CompleteBooking. Ignored otherwise (member bookings,
+    /// or a guest booking already Paid).</summary>
+    public class CompleteBookingRequest
+    {
+        public bool? MarkPaid { get; set; }
+        public decimal? AmountCollected { get; set; }
+        /// <summary>"Cash" | "Bank". Defaults to "Cash" if omitted.</summary>
+        public string? PaymentMethod { get; set; }
     }
 
     public class CheckInBookingRequest