Refactor site structure and add comprehensive interactive index

- Move Puzzles and Miscellany under Themes
- Add Contest Problems as new theme
- Create About page with comprehensive site information
- Create InteractiveIndex component with advanced filtering and sorting
- Update navigation to include Index, Themes, and About
- Add pagination (10 items per page) with search and tag filtering
- Update routing structure for new theme organization
- Remove standalone Puzzles and Miscellany pages
- Add new theme pages: /themes/puzzles, /themes/miscellany, /themes/contest-problems
- Update homepage to point to new interactive index
- Maintain consistent layout and styling across all new pages

src/components/Navigation.tsx

@@ -5,9 +5,9 @@ const Navigation = () => {
   const location = useLocation();
   
   const navItems = [
+    { name: "Index", path: "/index" },
     { name: "Themes", path: "/themes" },
-    { name: "Puzzles", path: "/puzzles" },
-    { name: "Miscellany", path: "/miscellany" }
+    { name: "About", path: "/about" }
   ];
 
   return (