[GUI] Status bar — real connection state, Live/Paper mode indicator, reconnect feedback

[jackby03]

Summary

The status bar shows a hard-coded "Connected" string. There is no real feedback about WebSocket state, reconnect attempts, active mode (Live vs Paper), or last error. This is misleading and makes debugging nearly impossible.

What needs to be done

• Subscribe to ConnectionStateChangedEvent (issue [Infra] Expand EventBus usage — decouple exchange, core and GUI through domain events #9) in the status bar renderer
• Show actual states: Connecting... | Connected | Reconnecting (3/5)... | Disconnected
• Add Live / Paper mode indicator (colored pill: orange for Paper, green for Live)
• Show last error message on hover or in a tooltip area
• Connection dot color matches state: green = connected, yellow = reconnecting, red = disconnected
• Latency (X ms) only shown when connected — hidden otherwise

Acceptance criteria

• Status bar reflects real ConnectionState from BinanceClient
• Live/Paper mode pill is visible at all times
• Reconnect attempt counter shown during reconnect: Reconnecting (2/5)...
• Status bar updates within one render frame of state change

Dependencies

• Issue [Exchange] WebSocket auto-reconnect with exponential backoff #2 (auto-reconnect, ConnectionState property)
• Issue [Infra] Expand EventBus usage — decouple exchange, core and GUI through domain events #9 (EventBus ConnectionStateChangedEvent)

References

• src/Omnijure.Visual/Rendering/StatusBarRenderer.cs