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>

public/icon-arrow-connector.svg

@@ -0,0 +1,10 @@
+<svg preserveAspectRatio="none" width="100%" height="100%" overflow="visible" style="display: block;" viewBox="0 0 40 12" fill="none" xmlns="http://www.w3.org/2000/svg">
+<g id="icon-arrow-connector" clip-path="url(#clip0_0_58)">
+<path id="Vector" d="M0 6H38M32 11L38 6L32 1" stroke="var(--stroke-0, #C9C9C9)" stroke-width="1.5" stroke-linecap="round" stroke-linejoin="round"/>
+</g>
+<defs>
+<clipPath id="clip0_0_58">
+<rect width="40" height="12" fill="white"/>
+</clipPath>
+</defs>
+</svg>