feat(themes): warn about animated themes on high-CPU setups (#1020)

* feat(themes): warn about animated themes on high-CPU setups

Show a warning icon + tooltip on animated themes (those defining
@keyframes) in the store and in Your Themes, on Linux setups where
animation is costly — the Nvidia WebKit quirk is active or compositing
is forced off. The Nvidia detection already runs once at startup; its
result is recorded (theme_animation.rs) and read via a new
theme_animation_risk command — no GPU re-probe. Display-only; never
shown off Linux. The animated flag comes from the registry (store) or
the theme CSS (Your Themes).

* docs(themes): note the animated-theme warning PR in the Theme Store entry

src/locales/en/settings.ts

@@ -391,6 +391,7 @@ export const settings = {
   tabThemes: 'Themes',
   themesYourThemesTitle: 'Your Themes',
   themesCvdTooltip: 'Colour-blind safe — deuteranopia, protanopia, tritanopia',
+  themeAnimationWarning: 'This theme uses animations that may raise CPU usage on your setup (Nvidia/Linux or compositing off).',
   themeStoreTitle: 'Theme Store',
   themeStoreSubmitText: 'Made your own theme? Share it with the community — more info in the themes repository.',
   themeStoreSubmitLink: 'Open the themes repository',