feat: add 服务端

PetWash.Api/Models/Package.cs

@@ -0,0 +1,10 @@
+namespace PetWash.Api.Models;
+
+public class Package
+{
+    public int Id { get; set; }
+    public string Name { get; set; } = string.Empty;
+    public decimal Price { get; set; }
+    public int DurationMinutes { get; set; }
+    public string Description { get; set; } = string.Empty;
+}