Add macOS .app bundle packaging with styled DMG

[Gabriel Dufresne (GabrielDuf)]

This pull request significantly improves the macOS packaging process for the project by introducing a proper .app bundle structure, adding a dedicated Info.plist, and using create-dmg for generating distributable DMG files. It also adds temporary ad-hoc code signing to the macOS build. Additionally, the workflow now restores dependencies for the correct runtime.

macOS packaging improvements:

• The GitHub Actions workflow now builds a proper macOS .app bundle, including the executable, resources, and an Info.plist file, enabling better integration with the macOS platform.
• A new scripts/macos/Info.plist file is added, providing essential metadata for the app bundle, such as version, identifier, and icon.
• The workflow installs create-dmg and uses it to generate a user-friendly DMG installer for macOS, replacing the previous manual hdiutil approach.
• Temporary ad-hoc code signing is applied to the app and its binaries to improve compatibility with macOS Gatekeeper (proper notarization to come later).

Build process improvement:

• The dotnet restore step now explicitly specifies the target runtime from the build matrix, ensuring dependencies are restored for the correct platform.