* wayland: small fixes

* fix double-free removing Wayland idle notify

* Translated using Weblate 

On systems that symlink /usr/sbin to /usr/bin, pkexec resolves the
mate-power-backlight-helper path canonically to /usr/bin but the polkit
annotation references /usr/sbin. This causes pkexec to require
authentication every time the brightness is changed.

This moves mate-power-backlight-helper to libexecdir and update the
polkit policy annotation and command call accordingly.

Fixes #411

After porting the indicator to SNI, the power icon rendered blank in the
notification area. The SNI host resolves icon names in its own process,
but our status icons are stored in the application's private icon theme
directory, so the host could never find them.

This fix points the indicator at the directory that contains our icon
theme so the notification area can resolve the battery icons again.

Adding Wayland support made ayatana-appindicator3 a hard requirement,
which breaks on systems without it (the previous tray icon is still
perfectly usable there).

This makes it optional and auto-detected at configure time, falling back
to the tray icon when the ayatana is unavailable.

Also make sure Wayland auto-detection only gets enables when every
Wayland dependency is actually present, instead of leaking the build
flag when an optional dependency is missing.

Fixes #432

* Preparations for Wayland backend

* Use system wayland-protocols

* Implement wlr-output-power-management

* Small refactors

* Small fixes

* Add vendored wlr protocol, build fixes

* Fix crash in mate-osd-window

* Port power manager indicator to SNI

* Fix appindicator init

* Positioning brightness applet's popup with gtk-layer-shell

Original-patch-by: @lukefromdc

* Add gtk-layer-shell dep

Bumps [actions/checkout](https://github.com/actions/checkout) from 6 to 7.
- [Release notes](https://github.com/actions/checkout/releases)
- [Changelog](https://github.com/actions/checkout/blob/main/CHANGELOG.md)
- [Commits](https://github.com/actions/checkout/compare/v6...v7)

---
updated-dependencies:
- dependency-name: actions/checkout
  dependency-version: '7'
  dependency-type: direct:production
  update-type: version-update:semver-major
...

Signed-off-by: dependabot[bot] <support@github.com>

Bumps [actions/cache](https://github.com/actions/cache) from 5 to 6.
- [Release notes](https://github.com/actions/cache/releases)
- [Changelog](https://github.com/actions/cache/blob/main/RELEASES.md)
- [Commits](https://github.com/actions/cache/compare/v5...v6)

---
updated-dependencies:
- dependency-name: actions/cache
  dependency-version: '6'
  dependency-type: direct:production
  update-type: version-update:semver-major
...

Signed-off-by: dependabot[bot] <support@github.com>

The notification spec only supports a handful of tags and <br> is not
one of them.

Fixes #272