Add project files.

Database/Entities/PuzzleCard.cs

@@ -0,0 +1,30 @@
+namespace ConnectionsAPI.Database.Entities
+{
+    public class PuzzleCard
+    {
+        /// <summary>
+        /// Primary key of the entity
+        /// </summary>
+        public int Id { get; set; }
+        
+        /// <summary>
+        /// The contents of this card (the word)
+        /// </summary>
+        public string Content { get; set; } = string.Empty;
+
+        /// <summary>
+        /// The initial position of this card on the grid
+        /// </summary>
+        public int Position { get; set; }
+
+        /// <summary>
+        /// The ID of the associated Connections category
+        /// </summary>
+        public int PuzzleCategoryId { get; set; }
+
+        /// <summary>
+        /// The associated category instance
+        /// </summary>
+        public virtual PuzzleCategory? PuzzleCategory { get; set; }
+    }
+}