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/practice/Pretest.tsx

@@ -23,7 +23,6 @@ const DOTS = [
 ];
 
 const STYLES = `
-  @import url('https://fonts.googleapis.com/css2?family=Nunito:wght@400;700;800;900&family=Nunito+Sans:wght@400;600;700&display=swap');
 
   :root { --content-max: 1100px; }
 
@@ -227,6 +226,7 @@ export const Pretest = () => {
   const { setSheetId, setMode, storeDuration, setQuestionCount } =
     useExamConfigStore();
   const user = useAuthStore((state) => state.user);
+  const token = useAuthStore((state) => state.token);
   const { sheetId } = useParams<{ sheetId: string }>();
   const navigate = useNavigate();
 
@@ -246,15 +246,9 @@ export const Pretest = () => {
   }
 
   useEffect(() => {
-    if (!user) return;
+    if (!user || !token) return;
     async function fetchSheet(id: string) {
-      const authStorage = localStorage.getItem("auth-storage");
-      if (!authStorage) return;
-      const {
-        state: { token },
-      } = JSON.parse(authStorage);
-      if (!token) return;
-      const data = await api.getPracticeSheetById(token, id);
+      const data = await api.getPracticeSheetById(token!, id);
       setPracticeSheet(data);
     }
     fetchSheet(sheetId!);