Add ToDo-Karten product page, fluid design tokens, and Navbar/Hero fixes

New /todo-cards page (Hero, How-it-works, Focus, Testimonials, Pricing)
built with the fluid clamp() token system (app/lib/fluid.ts) and
scroll-reveal animations (app/components/Reveal.tsx), matching styling
consistency with /challenge's testimonial section.

Navbar: page-aware active state and anchor-link navigation from any
route (not just "/"), fixed logo click to actually navigate instead of
silently rewriting the URL, fluid nav text size, custom hash-scroll
handling for cross-page anchor links.

Hero: responsive breakpoint fix for the text/image split at Tablet
widths, entrance animation for the brand's orange dot, removed a red
dot artifact from hero.png.

Also includes prior uncommitted work on About/Blog/Newsletter/Footer
and the cart lib (app/lib/cart.ts).

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

app/lib/cart.ts

@@ -0,0 +1,56 @@
+"use client";
+
+import { useEffect, useState } from "react";
+
+const CART_KEY = "ep_cart";
+const CART_EVENT = "ep-cart-updated";
+
+type CartItem = { id: string; qty: number };
+
+function readCart(): CartItem[] {
+  if (typeof window === "undefined") return [];
+  try {
+    const raw = window.localStorage.getItem(CART_KEY);
+    return raw ? JSON.parse(raw) : [];
+  } catch {
+    return [];
+  }
+}
+
+function writeCart(items: CartItem[]) {
+  window.localStorage.setItem(CART_KEY, JSON.stringify(items));
+  window.dispatchEvent(new Event(CART_EVENT));
+}
+
+export function getCartCount(): number {
+  return readCart().reduce((sum, item) => sum + item.qty, 0);
+}
+
+export function addToCart(id: string, qty = 1) {
+  const items = readCart();
+  const existing = items.find((i) => i.id === id);
+  if (existing) existing.qty += qty;
+  else items.push({ id, qty });
+  writeCart(items);
+}
+
+// Reactive cart item count — 0 until the client hydrates and reads
+// localStorage, then stays in sync across tabs ("storage") and same-tab
+// updates (the CART_EVENT dispatched by addToCart, which "storage" alone
+// doesn't fire for the tab that made the change).
+export function useCartCount(): number {
+  const [count, setCount] = useState(0);
+
+  useEffect(() => {
+    setCount(getCartCount());
+    const onUpdate = () => setCount(getCartCount());
+    window.addEventListener(CART_EVENT, onUpdate);
+    window.addEventListener("storage", onUpdate);
+    return () => {
+      window.removeEventListener(CART_EVENT, onUpdate);
+      window.removeEventListener("storage", onUpdate);
+    };
+  }, []);
+
+  return count;
+}