v2.6.0 — three new Speaches transcription aliases + explicit idle unload

New first-class LiteLLM aliases on both Speaches CPU and Speaches CUDA:

- local-speaches[-cuda]-whisper-large-v3-turbo
      deepdml/faster-whisper-large-v3-turbo-ct2 — ~8x faster than
      large-v3 at near-identical WER.

- local-speaches[-cuda]-crisper-whisper
      nyrahealth/faster_CrisperWhisper — verbatim transcription that
      preserves disfluencies, fillers, repetitions.

- local-speaches[-cuda]-parakeet-tdt-0.6b-v3
      istupakov/parakeet-tdt-0.6b-v3-onnx — multilingual (25 EU
      languages, upgrade from English-only v2).

Existing whisper-distil and parakeet-v2 aliases untouched.

Idle auto-unload made explicit: STT_MODEL_TTL / TTS_MODEL_TTL set on
both speaches services (default 600s, configurable via
SPEACHES_*_MODEL_TTL env vars). Acts as a safety net alongside the
LiteLLM resource manager's competing-job-arrival unload.