feat: add user accounts, authentication, and game history with Prisma 7

- Implement user registration and login with NextAuth v5 (email/password, JWT)
- Add authentication modal in UI with login/register tabs
- Create user profile screen showing game statistics and history
- Integrate Prisma 7 ORM with SQLite database for data persistence
- Store game results (mode, path, clicks, time) in database
- Auto-save completed games only when user is authenticated
- Separate business logic into reusable hooks (useSoloGame, useMultiGame)
- Organize UI into composable screen components (HomeScreen, SoloScreen, ProfileScreen, etc)
- Add session persistence across F5 refresh for solo and multiplayer
- Style auth modal, account button, and profile stats dashboard

app/api/register/route.ts

@@ -0,0 +1,23 @@
+import { NextRequest, NextResponse } from "next/server";
+import bcrypt from "bcryptjs";
+import { prisma } from "../../../lib/prisma";
+
+export async function POST(req: NextRequest) {
+  const { name, email, password } = await req.json() as { name?: string; email?: string; password?: string };
+
+  if (!name?.trim() || !email?.trim() || !password || password.length < 6) {
+    return NextResponse.json({ error: "Champs invalides (mot de passe min. 6 caractères)" }, { status: 400 });
+  }
+
+  const existing = await prisma.user.findUnique({ where: { email: email.toLowerCase() } });
+  if (existing) {
+    return NextResponse.json({ error: "Cet email est déjà utilisé" }, { status: 409 });
+  }
+
+  const hashed = await bcrypt.hash(password, 10);
+  const user = await prisma.user.create({
+    data: { name: name.trim(), email: email.toLowerCase(), password: hashed },
+  });
+
+  return NextResponse.json({ id: user.id, name: user.name, email: user.email }, { status: 201 });
+}