Add binary morphology commands

[yangfei]

Summary

• Add BinaryImage morphology operations: erode, dilate, open, and close.
• Use a fixed 3x3 square neighborhood with out-of-bounds pixels treated as false.
• Add Process menu commands for Erode, Dilate, Open, and Close.
• Accept only binary grayscale images with pixel values 0 or 255 for app morphology commands; unsupported grayscale input fails clearly.

Verification

• dotnet build ImageJCsharp.sln
• dotnet test tests/ImageJCsharp.Core.Tests/ImageJCsharp.Core.Tests.csproj
• dotnet test tests/ImageJCsharp.App.Tests/ImageJCsharp.App.Tests.csproj

Closes #23