An expired token was indistinguishable from a working one. set_token()
stamped token_expiry = now + 30 days every time a stored token was loaded,
so the expiry reset on every request and is_authenticated could never
return False. /cloud/status answered "connected" for as long as any token
existed, while every cloud call 401'd — and the user was shown Bambu's own
{"error": "Please login."} verbatim.
Bambu is now the authority: /cloud/status validates the token upstream
(cached 5m), and any 401 from any authenticated call durably records the
credential as dead via users.cloud_token_invalid_at, so MakerWorld, cloud
profiles, slicer presets and firmware checks all agree at once. An
unreachable Bambu is treated as unknown, never as expired, so an outage
cannot sign a working session out.
The user-facing message now names the Profiles page, where the Bambu Cloud
sign-in actually lives; the old text pointed at a Settings page that does
not exist. Same stale path corrected in the wiki.