fix: authentication flow with React Query migration

- Fix middleware management in apiClient to properly handle auth tokens
- Update ApiAuthProvider to correctly configure base URL and auth
- Add missing NextAuth API route handler at app/api/auth/[...nextauth]/route.ts
- Remove middleware ejection attempts (not supported by openapi-fetch)
- Use global variables to store current auth token and API URL
- Setup middleware once on initialization instead of repeatedly adding

This fixes the login/logout flow that was broken after migrating from
the useApi compatibility layer to native React Query hooks.

www/app/api/auth/[...nextauth]/route.ts

@@ -0,0 +1,6 @@
+import NextAuth from "next-auth";
+import { authOptions } from "../../../lib/auth";
+
+const handler = NextAuth(authOptions);
+
+export { handler as GET, handler as POST };