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/merci/page.tsx

@@ -0,0 +1,79 @@
+import Link from "next/link";
+import Button from "@/components/ui/Button";
+
+export default function MerciPage() {
+  return (
+    <main className="min-h-screen flex items-center justify-center px-4">
+      <div className="text-center max-w-lg">
+        {/* Success icon */}
+        <div className="w-20 h-20 gradient-bg rounded-full flex items-center justify-center mx-auto mb-8">
+          <svg
+            className="w-10 h-10 text-white"
+            fill="none"
+            stroke="currentColor"
+            viewBox="0 0 24 24"
+          >
+            <path
+              strokeLinecap="round"
+              strokeLinejoin="round"
+              strokeWidth={2}
+              d="M5 13l4 4L19 7"
+            />
+          </svg>
+        </div>
+
+        <h1 className="text-3xl md:text-4xl font-bold tracking-[-0.02em] mb-4">
+          Candidature <span className="gradient-text">envoyee !</span>
+        </h1>
+
+        <p className="text-white/60 text-lg mb-2">
+          Merci pour ta candidature. Notre equipe va etudier ton profil
+          attentivement.
+        </p>
+
+        <p className="text-white/40 mb-8">
+          Tu recevras une reponse par email sous 24 heures. Pense a verifier
+          tes spams !
+        </p>
+
+        {/* Étapes suivantes */}
+        <div className="bg-dark-light border border-dark-border rounded-[20px] p-6 mb-8 text-left">
+          <h2 className="text-white font-semibold mb-4">Prochaines etapes</h2>
+          <div className="space-y-4">
+            {[
+              {
+                step: "1",
+                title: "Analyse de ton profil",
+                desc: "Notre equipe evalue ta candidature",
+              },
+              {
+                step: "2",
+                title: "Email de confirmation",
+                desc: "Tu recois un email avec le lien de paiement",
+              },
+              {
+                step: "3",
+                title: "Acces au programme",
+                desc: "Tu commences ta formation immediatement",
+              },
+            ].map((item) => (
+              <div key={item.step} className="flex items-start gap-3">
+                <div className="w-7 h-7 gradient-bg rounded-lg flex items-center justify-center shrink-0 text-xs font-bold text-white">
+                  {item.step}
+                </div>
+                <div>
+                  <p className="text-white text-sm font-medium">{item.title}</p>
+                  <p className="text-white/40 text-xs">{item.desc}</p>
+                </div>
+              </div>
+            ))}
+          </div>
+        </div>
+
+        <Link href="/">
+          <Button variant="secondary">Retour a l&apos;accueil</Button>
+        </Link>
+      </div>
+    </main>
+  );
+}