fix: resolve bugs and improve frontend performance

- Fix register not resetting isLoading on success (causing login page to hang)
- Fix leaderboard streaks 400 error by forcing all_time timeframe
- Reorder routes so static paths match before dynamic practice/:sheetId
- Lazy-load QuestMap + Three.js (saves ~350KB gzip on initial load)
- Move KaTeX CSS to lazy import (only loads on math pages)
- Remove 28 duplicate Google Font @import lines from component CSS
- Add font preconnect + single stylesheet link in index.html
- Replace 8 unsafe JSON.parse(localStorage) calls with Zustand selectors
- Add global ErrorBoundary to prevent full-app crashes
- Extract arcTheme utilities to break static import cycle with QuestMap
- Merge Three.js + Troika into single chunk to fix circular dependency

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

src/pages/student/StudentLayout.tsx

@@ -57,8 +57,7 @@ const QUEST_NAV_ITEMS = NAV_ITEMS.map((item) =>
 );
 
 const STYLES = `
-  @import url('https://fonts.googleapis.com/css2?family=Nunito:wght@700;800;900&family=Cinzel:wght@700&display=swap');
-  @import url('https://fonts.googleapis.com/css2?family=Sorts+Mill+Goudy:ital@0;1&display=swap');
+
 
   /* ══ DEFAULT dock (cream frosted glass) ══ */
   .sl-dock-wrap {