Add Phase 0: sign-up, login, and profile

- Next.js (App Router) + TypeScript + Tailwind
- Prisma + SQLite for the User model
- Sign-up with 18+ age gate, email/password validation (zod), bcrypt hashing
- Login via NextAuth credentials provider, JWT sessions
- Protected /profile route (view + edit name/bio)

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01VL5YUEf2B9LG4xdVUQwcSg

postcss.config.mjs

@@ -0,0 +1,9 @@
+/** @type {import('postcss-load-config').Config} */
+const config = {
+  plugins: {
+    tailwindcss: {},
+    autoprefixer: {},
+  },
+};
+
+export default config;