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/Rewards.tsx

@@ -31,7 +31,6 @@ 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; }
 
@@ -415,6 +414,7 @@ const EmptyState = () => (
 
 export const Rewards = () => {
   const user = useAuthStore((state) => state.user);
+  const token = useAuthStore((state) => state.token);
   const [time, setTime] = useState("today");
   const [activeTab, setActiveTab] = useState<TabId>("xp");
   const [leaderboard, setLeaderboard] = useState<Leaderboard | undefined>();
@@ -431,20 +431,15 @@ export const Rewards = () => {
 
   useEffect(() => {
     const fetchData = async () => {
-      if (!user) return;
-      const authStorage = localStorage.getItem("auth-storage");
-      if (!authStorage) return;
-      const parsed = JSON.parse(authStorage) as {
-        state?: { token?: string };
-      } | null;
-      const token = parsed?.state?.token;
-      if (!token) return;
+      if (!user || !token) return;
       try {
         setLoading(true);
+        const timeframe =
+          activeTab === "streaks" ? "all_time" : (TIME_MAP[time] ?? "daily");
         const response = await api.fetchLeaderboard(
           token,
           activeTab,
-          TIME_MAP[time] ?? "daily",
+          timeframe,
         );
         setLeaderboard(response);
         // ✅ FIX 1: Guard against null user_rank before accessing its properties
@@ -563,9 +558,13 @@ export const Rewards = () => {
             </div>
 
             <DropdownMenu>
-              <DropdownMenuTrigger asChild>
-                <button className="rw-filter-btn">
-                  {formatTimeLabel(time)} <ChevronDown size={13} />
+              <DropdownMenuTrigger asChild disabled={activeTab === "streaks"}>
+                <button
+                  className="rw-filter-btn"
+                  style={activeTab === "streaks" ? { opacity: 0.5, cursor: "not-allowed" } : undefined}
+                >
+                  {activeTab === "streaks" ? "All Time" : formatTimeLabel(time)}{" "}
+                  <ChevronDown size={13} />
                 </button>
               </DropdownMenuTrigger>
               <DropdownMenuContent