Этап 2

Minint.Core/Services/IFloodFillService.cs

@@ -0,0 +1,12 @@
+using Minint.Core.Models;
+
+namespace Minint.Core.Services;
+
+public interface IFloodFillService
+{
+    /// <summary>
+    /// Flood-fills a contiguous region of identical color starting at (<paramref name="x"/>, <paramref name="y"/>)
+    /// with <paramref name="newColorIndex"/>. Uses 4-connectivity (up/down/left/right).
+    /// </summary>
+    void Fill(MinintLayer layer, int x, int y, int newColorIndex, int width, int height);
+}