Merge commit 'd13d7b4566d551d027830f7dfc987ba3a8e2dd4f' into glitch-soc/merge-upstream

Conflicts are too numerous to list, but they are all caused by upstream's
theming changes and all have to do with the differences between upstream and
glitch-soc in the theming systems.

They were all manually resolved by adapting the relevant code.

app/javascript/skins/vanilla/contrast/common.scss

@@ -1 +0,0 @@
-@use '@/styles/contrast';

app/javascript/skins/vanilla/contrast/names.yml

@@ -1,12 +0,0 @@
-en:
-  skins:
-    vanilla:
-      contrast: High contrast
-cs:
-  skins:
-    vanilla:
-      contrast: Vysoký kontrast
-es:
-  skins:
-    vanilla:
-      contrast: Alto contraste

app/javascript/skins/vanilla/mastodon-light/common.scss

@@ -1 +0,0 @@
-@use '@/styles/mastodon-light';

app/javascript/skins/vanilla/mastodon-light/names.yml

@@ -1,12 +0,0 @@
-en:
-  skins:
-    vanilla:
-      mastodon-light: Mastodon (light)
-cs:
-  skins:
-    vanilla:
-      mastodon-light: Mastodon (světlý)
-es:
-  skins:
-    glitch:
-      mastodon-light: Mastodon (claro)