Improved repository configuration by updating `.gitattributes` to:
- Normalize line endings automatically.
- Define diff behavior for C# files and common document formats.
- Add optional merge driver settings for Visual Studio project files.
- Treat image files as binary.
Enhanced `.gitignore` to:
- Exclude Visual Studio-specific files, build outputs, and temporary files.
- Ignore files generated by add-ons, testing frameworks, and tools.
- Add project-specific exclusions for `EnvelopeGenerator`.
These changes enhance maintainability, reduce clutter, and prevent unnecessary files from being committed.
