Fix WebSocket URL using wrong config field (baseUrl instead of websocketUrl)

[Copilot]

PR #2 moved WS URL construction server-side but accidentally used atlasConfig.baseUrl (the web app's own origin) instead of atlasConfig.websocketUrl (the Atlas API URL with ws:///wss:// protocol). This broke all WebSocket functionality. PR #3 kept the same root cause.

Change

• getWebSocketToken handler — swap baseUrl.replace(/^http/, "ws") for websocketUrl, which is already stored at setup time as atlasUrl with the correct WebSocket protocol:

// Before (broken — points at the web app, not the Atlas API)
wsUrl: `${configManager.getAtlasConfig()?.baseUrl!.replace(/^http/, "ws")}/api/v1/servers/${serverId}/ws`

// After — matches what the original client-side code used before PR #2
wsUrl: `${configManager.getAtlasConfig()?.websocketUrl}/api/v1/servers/${serverId}/ws`

websocketUrl is set during setup as atlasUrl.replace("https://", "wss://").replace("http://", "ws://"), making it the correct base for Atlas API WebSocket connections.