Rename SawCut library to CutList.Core

Rename the core library project from SawCut to CutList.Core for consistent
branding across the solution. This includes:
- Rename project folder and .csproj file
- Update namespace from SawCut to CutList.Core
- Update all using statements and project references

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

CutList.Core/Nesting/EngineFactory.cs

@@ -0,0 +1,19 @@
+namespace CutList.Core.Nesting
+{
+    /// <summary>
+    /// Default implementation of IEngineFactory that creates AdvancedFitEngine instances.
+    /// Can be extended to support different engine types based on configuration.
+    /// </summary>
+    public class EngineFactory : IEngineFactory
+    {
+        public IEngine CreateEngine(double stockLength, double spacing, int maxBinCount)
+        {
+            return new AdvancedFitEngine
+            {
+                StockLength = stockLength,
+                Spacing = spacing,
+                MaxBinCount = maxBinCount
+            };
+        }
+    }
+}