page/dashboard-page: build real-time dashboard UI

[Rend1027]

• Create a new route/page for the dashboard (e.g., /dashboard)
• Design layout to display real-time listener activity nearby
• For each active session:
  - Show user's display name (if available)
  - Show what song they are currently or recently listening to
  - Optional: display avatar/icon or generated emoji
  - Include 🎧 emoji or icon for style

Use dummy data first (or wire up to real ListeningSessions if ready)
Refer back to our wireframe in the LocalBeats document.

This page will serve as the heartbeat of the app, showing real-time music activity nearby — the foundation for active listeners and community-based trends.