Add Connection Status Indicator

[w2naf]

Description

Add a visual indicator showing whether the dashboard is connected to the backend API and receiving data. This addresses requirement FR-UI-03.

Acceptance Criteria

• Status indicator visible in the UI (e.g., header bar or footer)
• Shows connected/disconnected/error states
• Updates automatically when connection state changes
• Non-intrusive — does not block the main dashboard view

Requirements Reference

• FR-UI-03: Connection status indicators

Blocked By

• Install, Test, and Debug Current DXDashboard on W3USR System #31 (Install, Test, and Debug Current DXDashboard)

Milestone

Milestone 1: Minimal Working System (Feb 28)