DATA-2: amendments — GerbilStatus.ForSale, Contact structured fields, 73-variety seed

- GerbilStatus += ForSale ("Abzugeben", FEAT-12 sale listing); enum-as-string, no DB change.
- Contact: contactInfo -> structured email/phone/address (FEAT-13 sale contracts); name/notes kept.
- ColorVariety seed 18 -> 73 from Kevin's GEN-2 colorVarietySeed.generated.json (18 frozen first).
- Regenerated InitialCreate migration (Contacts email/phone/address cols, 73 seed rows).

GerbilManagerWebAPI/Models/Contact.cs

@@ -11,7 +11,9 @@ namespace GerbilManagerWebAPI.Models
         [Key]
         public Guid Id { get; set; }
         public required string Name { get; set; }
-        public string? ContactInfo { get; set; }
+        public string? Email { get; set; }
+        public string? Phone { get; set; }
+        public string? Address { get; set; }
         public string? Notes { get; set; }
     }
 }

GerbilManagerWebAPI/Models/GerbilStatus.cs

@@ -5,6 +5,8 @@ namespace GerbilManagerWebAPI.Models
     {
         Active = 0,
         Deceased = 1,
-        GivenAway = 2
+        GivenAway = 2,
+        /// <summary>Alive, at home, offered for Abgabe ("Abzugeben"). Drives FEAT-12 sale listing.</summary>
+        ForSale = 3
     }
 }