feat: initial project structure with Snake.Core, CLI and Avalonia skeleton

Snake.Core/Food.cs

@@ -0,0 +1,38 @@
+namespace Snake.Core;
+
+public sealed class Food
+{
+    private readonly Random _random;
+
+    public Food(Board board, IEnumerable<Position> occupiedPositions, Random? random = null)
+    {
+        _random = random ?? Random.Shared;
+        Board = board;
+        Respawn(occupiedPositions);
+    }
+
+    public Board Board { get; }
+
+    public Position Position { get; private set; }
+
+    public void Respawn(IEnumerable<Position> occupiedPositions)
+    {
+        var occupied = occupiedPositions.ToHashSet();
+        var freeCells = new List<Position>();
+
+        for (var y = 0; y < Board.Height; y++)
+        {
+            for (var x = 0; x < Board.Width; x++)
+            {
+                var position = new Position(x, y);
+                if (!occupied.Contains(position))
+                    freeCells.Add(position);
+            }
+        }
+
+        if (freeCells.Count == 0)
+            throw new InvalidOperationException("No free cells available for food.");
+
+        Position = freeCells[_random.Next(freeCells.Count)];
+    }
+}