/admin/api/models is served by the primary engine and ran list_models()
with the per-engine assignment filter, so models pinned to a secondary
engine (whisper-servers configured with engine=radeon) were dropped. That
emptied the whisper-server config form and left those models unmatched in
the loaded-status check, so they never showed as loaded.

Add list_models(all_engines=True) to bypass _entry_assigned, and call it
from the admin model list. Combined with the whisper-servers now reported
in /internal/engine-state, the radeon whisper-servers reappear in their own
form and show as loaded.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>