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

lib/prisma.ts

@@ -0,0 +1,16 @@
+import Database from "better-sqlite3";
+import { PrismaBetterSqlite3 } from "@prisma/adapter-better-sqlite3";
+import { PrismaClient } from "./generated/prisma/client";
+
+const globalForPrisma = globalThis as unknown as { prisma?: PrismaClient };
+
+function createPrisma() {
+  const adapter = new PrismaBetterSqlite3({ url: "./wikirace.db" });
+  return new PrismaClient({ adapter });
+}
+
+export const prisma = globalForPrisma.prisma ?? createPrisma();
+
+if (process.env.NODE_ENV !== "production") {
+  globalForPrisma.prisma = prisma;
+}