GUI: Migrate to PySide6 (Enables ARM/Apple Silicon support)

[therohityadav]

Fixes #822

This PR migrates the GUI dependencies from PySide2 to PySide6.
This upgrade enables native builds for ARM architectures (macOS Apple Silicon, Linux aarch64) and removes the restriction on Python 3.10+.

Changes:

• Dependencies: Updated pyproject.toml and setup.py to use PySide6.
• Generator: Updated contrib/generate-ui.sh to use pyside6-uic.
• Code Migration:
  • Replaced app.exec_() with app.exec() (Python 3 standard).
  • Updated imports (Moved QAction, QKeySequence to QtGui).
  • Replaced deprecated QRegExp with QRegularExpression.

Testing:

• I verified this on Linux x86_64. The GUI launches and operates correctly.
• It needs verification on macOS (Apple Silicon) as I do not have access to that hardware.

[Sjors]

Concept ACK.

I'll probably test this after #819.