v1 – Update app-next with new UI

[HelderMendes]

Description

This PR introduces the new Next.js frontend implementation in app-next. It includes a modern UI, improved search functionality using Elasticsearch, and a responsive design.

Note: This is a clean PR replacing #361, containing ONLY the changes within app-next to avoid whitespace and unrelated file noise.

Key Changes

• New UI: Implemented a modern, responsive design using Tailwind CSS and Radix UI.
• Search: Integrated Elasticsearch for datasets, tasks, flows, and runs.
• Components: Added reusable components for data tables, filters, and navigation.
• Routing: Set up Next.js app router structure.