desktop: add notification center, better cursors

[humaidq-tii]

Description of changes

This replaces mako with swaynotificationcenter, and makes cursors on the desktop and Qt apps consistent with GTK.

• Makes cursor consistent with apps
  • This means the cursor theme won't change anymore when moving cursor from app->desktop.
  • Qt applications and chromium would load also the proper font.
• Adds swaynotificationcenter
  • Adds patch for theme. The 'scss' file needs to be compiled, in the future we might make our own package for the swaync theme if needed.
  • Cog icon now loads the notification center, showing notifications.
  • Button for wifi settings is now in the notification center.

Checklist for things done

• Summary of the proposed changes in the PR description
• More detailed description in the commit message(s)
• Commits are squashed into relevant entities - avoid a lot of minimal dev time commits in the PR
• Contribution guidelines followed
• Ghaf documentation updated with the commit - https://tiiuae.github.io/ghaf/
• PR linked to architecture documentation and requirement(s) (ticket id)
• Test procedure described (or includes tests). Select one or more:
  • Tested on Lenovo X1 x86_64
  • Tested on Jetson Orin NX or AGX aarch64
  • Tested on Polarfire riscv64
• Author has run make-checks and it passes
• All automatic Github Action checks pass - see actions
• Author has added reviewers and removed PR draft status
• Change requires full re-installation
• Change can be updated with nixos-rebuild ... switch

Instructions for Testing

• List all targets that this applies to:
• Is this a new feature
  • List the test steps to verify:
• If it is an improvement how does it impact existing functionality?

[humaidq-tii]

Closing in favour of #790, cursor fix included in #791