Switch from SuperTokens to NextAuth.js

BREAKING CHANGE: Replace SuperTokens with NextAuth.js

Why:
- SuperTokens had persistent Traefik routing issues
- SSL certificate not issuing correctly
- Complex infrastructure (separate container)
- NextAuth runs in Next.js app (simpler, no separate service)

Changes:
- Install next-auth, @auth/prisma-adapter, prisma
- Create NextAuth API route: app/api/auth/[...nextauth]/route.ts
- Add Prisma schema for NextAuth tables (users, sessions, accounts)
- Update auth page to use NextAuth signIn()
- Remove all SuperTokens code and dependencies
- Keep same Google OAuth (just simpler integration)

Benefits:
- No separate auth service needed
- No Traefik routing issues
- Sessions stored in Montreal PostgreSQL
- Simpler configuration
- Battle-tested, widely used

All authentication data stays in Montreal!

Co-authored-by: Cursor <cursoragent@cursor.com>

lib/auth/authOptions.ts

@@ -0,0 +1,33 @@
+import { NextAuthOptions } from "next-auth";
+import GoogleProvider from "next-auth/providers/google";
+import { PrismaAdapter } from "@auth/prisma-adapter";
+import { PrismaClient } from "@prisma/client";
+
+const prisma = new PrismaClient();
+
+export const authOptions: NextAuthOptions = {
+  adapter: PrismaAdapter(prisma),
+  providers: [
+    GoogleProvider({
+      clientId: process.env.GOOGLE_CLIENT_ID || "",
+      clientSecret: process.env.GOOGLE_CLIENT_SECRET || "",
+    }),
+  ],
+  pages: {
+    signIn: "/auth",
+    error: "/auth",
+  },
+  callbacks: {
+    async session({ session, user }) {
+      if (session.user) {
+        session.user.id = user.id;
+      }
+      return session;
+    },
+  },
+  session: {
+    strategy: "database",
+    maxAge: 30 * 24 * 60 * 60, // 30 days
+  },
+  secret: process.env.NEXTAUTH_SECRET,
+};