Scaffold V1: auth, profils et leaderboard

Next.js 16 + Tailwind + Supabase (Auth, Postgres, Storage). Connexion
par pseudo/mot de passe via email interne dérivé, RLS avec points
protégés au niveau colonne, pages login/signup/leaderboard/profile.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

src/proxy.ts

@@ -0,0 +1,10 @@
+import { type NextRequest } from "next/server";
+import { updateSession } from "@/lib/supabase/middleware";
+
+export async function proxy(request: NextRequest) {
+  return updateSession(request);
+}
+
+export const config = {
+  matcher: ["/((?!_next/static|_next/image|favicon.ico|.*\\.(?:svg|png|jpg|jpeg|gif|webp)$).*)"],
+};