feat: futuristic theme ladder + stacked landing banner

Add three opt-in dark themes (BooCode+, BooCode Classic, BooCode
Override) plus an in-place Ember polish, on a class-scoped effects
engine: matrix rain, a neon grid field, and frosted glass, all gated
by a localStorage "Animated background" toggle and prefers-reduced-
motion. Extend the server theme_id whitelist so the new ids persist,
and replace the Home landing wordmark with the stacked mascot +
wordmark banner.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

apps/server/src/routes/settings.ts

@@ -45,6 +45,10 @@ const THEME_IDS = [
   'cobalt',
   'midnight-sapphire',
   'ember',
+  // futuristic ladder (opt-in) — kept in sync with apps/web/src/lib/theme.ts THEMES
+  'boocode-plus',
+  'boocode-classic',
+  'boocode-override',
 ] as const;
 
 const THEME_MODES = ['dark', 'light', 'system'] as const;