Rename /lebensuhr to /7-tage-klarheits-check, update CTA/content copy

Renames the route, its canonical/OG metadata, Navbar's active-route
list, and the testimonials page filter to match. Also updates CTA
copy ("Klarheits-Check starten"), the "So funktioniert" heading, the
"3. Umsetzen" step text, and the breadcrumb label.

app/components/Hero.tsx

@@ -103,7 +103,7 @@ export function Hero() {
               image/banner above it on true Mobile), left-aligned with the
               rest of the text column again from sm: up. */}
           <Link
-            href="/lebensuhr"
+            href="https://einfach-produktiv.mk360.de/7-tage-klarheits-check"
             className="flex gap-4 items-center justify-center overflow-clip px-6 py-3 rounded-sm shrink-0 max-w-full bg-brand hover:brightness-95 active:scale-[0.97] transition-all self-center sm:self-auto"
           >
             {/* Letting this wrap to two lines below lg: (tried 2026-07-24)

app/components/Navbar.tsx

@@ -63,7 +63,7 @@ function getNavLinks(singleActiveProduct: boolean) {
 // /der-eine and /tasse-die-pause (both bespoke product detail pages, same
 // "own route, not nested" shape as /todo-cards) added here for the same
 // reason (2026-08-25).
-const WERKZEUGE_ROUTES = ["/todo-cards", "/lebensuhr", "/newsletter", "/der-eine", "/tasse-die-pause"];
+const WERKZEUGE_ROUTES = ["/todo-cards", "/7-tage-klarheits-check", "/newsletter", "/der-eine", "/tasse-die-pause"];
 
 function isNavLinkActive(href: string, pathname: string, activeSection: string): boolean {
   if (href === "#werkzeuge") {