Add image processing benchmarks and UI folder open buttons

- Added MaddoShared.Benchmarks project with BenchmarkDotNet for comprehensive image processing performance tests (parallel, chunk, size, stress).
- Included helper for generating test images and custom configs to ensure InProcess toolchain for .NET Windows compatibility.
- Added cross-platform scripts to run benchmarks easily.
- Updated .gitignore for benchmark artifacts and temp files.
- Exposed GetFilesToProcessPublic in ImageCreationStuff for testability.
- Added file name sanitization in ImageCreatorSharp to prevent IO errors.
- Enhanced WinForms UI: added "Open" buttons for source/destination folders, handled folder opening in Explorer, and improved user messaging and layout.
- Updated solution file to include new benchmark project.

MaddoShared.Benchmarks/Program.cs

@@ -0,0 +1,35 @@
+using BenchmarkDotNet.Configs;
+using BenchmarkDotNet.Jobs;
+using BenchmarkDotNet.Running;
+using BenchmarkDotNet.Toolchains.InProcess.Emit;
+using System;
+using System.Linq;
+
+namespace MaddoShared.Benchmarks;
+
+internal class Program
+{
+    static void Main(string[] args)
+    {
+        // Check if --job argument is provided
+        bool hasJobArg = args.Any(a => a.Contains("--job"));
+        
+        if (hasJobArg)
+        {
+            Console.WriteLine("Note: Overriding --job argument to use InProcess toolchain");
+            Console.WriteLine("This is required to avoid net10.0 vs net10.0-windows compatibility issues.");
+            Console.WriteLine();
+            
+            // Remove --job arguments and add our own InProcess config
+            args = args.Where(a => !a.StartsWith("--job") && a != "dry" && a != "short").ToArray();
+        }
+        
+        // Create configuration that always uses InProcess toolchain
+        var config = DefaultConfig.Instance
+            .WithOptions(ConfigOptions.DisableOptimizationsValidator)
+            .WithOptions(ConfigOptions.KeepBenchmarkFiles);
+
+        // Run benchmarks - each class has [Config(typeof(InProcessConfig))] which provides InProcess toolchain
+        BenchmarkSwitcher.FromAssembly(typeof(Program).Assembly).Run(args, config);
+    }
+}