Future linting improvements

[deltragon]

Followup to https://github.com/slgobinath/SafeEyes/pull/615.

• [ ] Forbid + for string concatenation
• [ ] Sort/format imports Needs to figure out how to deal with gi.require_version calls mixed in
• [ ] Improve doc comments, remove "obvious" ones this one might need to go into the style guide, if we can't check it automatically
• [ ] Use constants instead of magic values - https://docs.astral.sh/ruff/rules/magic-value-comparison/