bump: doxygen 1.15.0 -> 1.16.1

[mutalibmohammed]

Main Changes:

• Updated the default Doxygen version from 1.15.0 to 1.16.1 for all platforms in the extension configuration.
• Updated the download logic for macOS to support separate DMG files for Intel and ARM architectures, with a fallback to the previous universal DMG naming for older versions.
• Updated the CI workflow to use Doxygen version 1.16.1 by default.