Add GameDataController for item icon retrieval; update GameItemsRepository and GameItemService for new action effects

Repositories/GameItemsRepository.cs

@@ -22,6 +22,16 @@ namespace PetCompanion.Repositories
             return _context.GameItems;
         }
 
+        public byte[] GetItemIcon(int itemId)
+        {
+            if (_context.GameItems.Find(itemId) == null)
+            {
+                throw new Exception("Item not found");
+            }
+
+            return File.ReadAllBytes($"game-data/item/icons/{itemId}.png");
+        }
+
         public void Add(GameItem item)
         {
             _context.GameItems.Add(item);