Add action gathering functionality: implement ActionGathered model and repository, update Pet model and services, and enhance GameItemsRepository with item retrieval methods.

Models/ActionGathered.cs

@@ -0,0 +1,22 @@
+using System.ComponentModel.DataAnnotations;
+using System.ComponentModel.DataAnnotations.Schema;
+using System.Text.Json.Serialization;
+
+namespace PetCompanion.Models
+{
+    public class ActionGathered
+    {
+        [DatabaseGenerated(DatabaseGeneratedOption.Identity)]
+        [Key]
+        public int Id { get; set; }
+        [ForeignKey("Pet")]
+        public string PetId { get; set; }
+        public string? Resource { get; set; }
+        [ForeignKey("GameItem")]
+        public int? ItemId { get; set; }
+        public int Amount { get; set; }
+        [JsonIgnore]
+        public virtual Pet Pet { get; set; }
+        public virtual GameItem? GameItem { get; set; }
+    }
+}