Pyproject metadata

[phw]

Summary

• This is a…
  • Bug fix
  • Feature addition
  • Refactoring
  • Minor / simple change (like a typo)
  • Other
• Describe this change in 1-2 sentences:

Problem

This is one step in the goal to nove package metadata into pyproject.toml and reduce code in setup.py.

Solution

• Define [project] section in pyproject.toml and declare package metadata there. Remove the corresponding data from setup.py
• Remove obsolete code from setup.py
• Define setuptools package and extension in pyproject.toml and remove custom code from setup.py
• Unified the short app description to be the same in Python package metadata and appstream metadata.

Not handled here:

• Requirements are still defined in requirements.txt and read from there. This can be changed once we move to e.g. ruff
• Entry points: This is currently highly system dependent and for now handled dynamically by setup.py.
• Data files: Handling of locale translation files will be changed and done in a separate PR. The additional handling for system wide assets (which are not directly loaded by the application) on Unix systems (.desktop file, app icon, appstream metadata) will most likely stay in setup.py as part of the packaging process.
• Custom commands in setup.py: In he future those could be moved to a separate task handler, at least the ones that are not invoked during build. Custom commands that are invoked during build likely better stay in setup.py to avoid additional build-time dependencies.

[zas]

LGTM