GuestLog - StayEntry - Initial Implementation

- Added new entity "StayEntry" to log stays of guests.
- Added pages for StayEntry management (List and creation).
- New DataList for PaymentMethods.
- Other general changes and improvements.

src/Somnia.GuestLog/Models/Entities/StayEntry.cs

@@ -0,0 +1,24 @@
+namespace Somnia.GuestLog.Models.Entities;
+
+public class StayEntry : BaseEntity
+{
+    public long Id { get; set; }
+
+    public required DateTime DateIn { get; set; }
+    public required DateTime DateOut { get; set; }
+
+    public required int RoomCount { get; set; }
+    public string? RoomNumber { get; set; }
+
+    public required string PaymentMethod { get; set; }
+
+    public virtual ICollection<GuestDocument> GuestDocuments { get; } = [];
+
+
+    //Generated Properties.
+    public required DateTime CreateTime { get; set; }
+    public required DateTime UpdateTime { get; set; }
+
+
+    public override string GetFullKey() => $"{Id}";
+}