feat(db): add auth callback with redirect

app/auth/callback/route.ts

@@ -0,0 +1,20 @@
+import { NextResponse } from "next/server";
+
+import { createClient } from "@/db/server";
+
+export async function GET(request: Request) {
+  // The `/auth/callback` route is required for the server-side auth flow implemented
+  // by the SSR package. It exchanges an auth code for the user's session.
+  // https://supabase.com/docs/guides/auth/server-side/nextjs
+  const requestUrl = new URL(request.url);
+  const code = requestUrl.searchParams.get("code");
+  const origin = requestUrl.origin;
+
+  if (code) {
+    const supabase = createClient();
+    await supabase.auth.exchangeCodeForSession(code);
+  }
+
+  // URL to redirect to after sign up process completes
+  return NextResponse.redirect(`${origin}/protected`);
+}