Route image model tests to /api/v1/images/generations and STT to
/api/v1/audio/transcriptions instead of forcing all non-embedding
models through chat completions. Adds kind-aware pingModelByKind,
hf->huggingface alias, and silent WAV sample for STT reachability.
Scoped to dashboard/internal model testing only; runtime inference
routing is unchanged.
Author: yicone <yicone@gmail.com>
Closes#1628