Summary: * Make colors for `hoverselectedgrey` and `hoverselectedblue` in Dark Mode not to use Default Mode colors. * Replace hardcoded text color for for strike-through links (`a.handle-status-closed`) `#676767` with close-enough variable `{$lightgreytext}`, and in case of hovering such a strike-through link `#19558D` with `{$darkbluetext}`. Refs T15056 Test Plan: * Go to http://phorge.localhost/settings/panel/display/ and set `Accessibility` to `Dark Mode (Experimental)` * Create notifications, have setup issues, etc. Open top bar menu items and hover. Find a strike-through link and hover. * Probably also check other pages for `a.handle-status-closed` but I'm too lazy for that. Reviewers: O1 Blessed Committers, mainframe98 Reviewed By: O1 Blessed Committers, mainframe98 Subscribers: mainframe98, tobiaswiese, valerio.bozzolan, Matthew, Cigaryno Maniphest Tasks: T15056 Differential Revision: https://we.phorge.it/D26393