Get Central Robot Status

Proxy to the central signaling server's /api/robot-status endpoint.

Uses the stored HF token server-side so the desktop frontend never sees the raw token. The frontend polls this to know whether any of the user's robots is currently held by a remote JS app, and if so which one (so it can show "In use by Hand Tracker" in the UI).

Response shape: { "available": bool, "robots": [...], "reason": str? }

available is false when:

• no HF token stored (user not logged in)
• central server is unreachable / returned an error Callers should treat available: false as "unknown, don't block".