fix: remove middleware and route groups to fix Vercel deployment

- Remove middleware.ts entirely (caused __dirname ReferenceError in Edge)
- Auth protection handled by dashboard layout.tsx (server-side redirect)
- Move pages out of (marketing) and (auth) route groups to fix 404 on /
- Keep (protected) route group for dashboard/formations/profil shared layout

https://claude.ai/code/session_01H2aRGDaKgarPvhay2HxN6Y

app/page.tsx

@@ -0,0 +1,23 @@
+import Navbar from "@/components/marketing/Navbar";
+import Hero from "@/components/marketing/Hero";
+import Testimonials from "@/components/marketing/Testimonials";
+import PersonaCards from "@/components/marketing/PersonaCards";
+import Method from "@/components/marketing/Method";
+import Pricing from "@/components/marketing/Pricing";
+import FAQ from "@/components/marketing/FAQ";
+import Footer from "@/components/marketing/Footer";
+
+export default function LandingPage() {
+  return (
+    <main className="min-h-screen">
+      <Navbar />
+      <Hero />
+      <Testimonials />
+      <PersonaCards />
+      <Method />
+      <Pricing />
+      <FAQ />
+      <Footer />
+    </main>
+  );
+}