ui : let a remote model report its own status
Listings dropped the load state they carry, status lookups only ever read
the local router rows, and the status feed belongs to the local server, so
a model loaded on an external llama-server stayed unloaded as far as the
UI knew. The state now travels with the model, lookups resolve the backend
that serves it, and an external operation settles by asking that backend
for its list until the status lands.
Assisted-by: pi:llama.cpp/DeepSeek-V4.1-Flash
