Refactor theme structure

Add new themes under Discrete Math, move binary interactive, and remove School Connect.

src/pages/theme-pages/discrete-math/Counting.tsx

@@ -0,0 +1,12 @@
+import ComingSoon from "@/components/ComingSoon";
+
+const Counting = () => {
+  return (
+    <ComingSoon 
+      title="Counting"
+      description="Explore combinatorics, permutations, combinations, and advanced counting principles through visual tools and interactive exercises."
+    />
+  );
+};
+
+export default Counting;