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

lib/supabase/middleware.ts

@@ -1,59 +0,0 @@
-import { createServerClient } from "@supabase/ssr";
-import { NextResponse, type NextRequest } from "next/server";
-
-// Middleware Supabase pour refresh des tokens auth
-export async function updateSession(request: NextRequest) {
-  let supabaseResponse = NextResponse.next({
-    request,
-  });
-
-  const supabase = createServerClient(
-    process.env.NEXT_PUBLIC_SUPABASE_URL!,
-    process.env.NEXT_PUBLIC_SUPABASE_ANON_KEY!,
-    {
-      cookies: {
-        getAll() {
-          return request.cookies.getAll();
-        },
-        setAll(cookiesToSet) {
-          cookiesToSet.forEach(({ name, value }) =>
-            request.cookies.set(name, value)
-          );
-          supabaseResponse = NextResponse.next({
-            request,
-          });
-          cookiesToSet.forEach(({ name, value, options }) =>
-            supabaseResponse.cookies.set(name, value, options)
-          );
-        },
-      },
-    }
-  );
-
-  const {
-    data: { user },
-  } = await supabase.auth.getUser();
-
-  // Rediriger vers login si pas connecté et route protégée
-  if (
-    !user &&
-    request.nextUrl.pathname.startsWith("/dashboard")
-  ) {
-    const url = request.nextUrl.clone();
-    url.pathname = "/login";
-    return NextResponse.redirect(url);
-  }
-
-  // Rediriger vers dashboard si déjà connecté et sur login/register
-  if (
-    user &&
-    (request.nextUrl.pathname === "/login" ||
-      request.nextUrl.pathname === "/register")
-  ) {
-    const url = request.nextUrl.clone();
-    url.pathname = "/dashboard";
-    return NextResponse.redirect(url);
-  }
-
-  return supabaseResponse;
-}