v2.7.0 — asr-canary STT service + cuda-stt group split + parakeet fix

- New aigate/asr-canary/ FastAPI wrapper (OpenAI-compat transcribe +
  speaches-compat /api/ps). CPU: canary-180m-flash. CUDA:
  canary-180m-flash, canary-1b-flash, canary-qwen-2.5b (SALM).
- Pull-sidecar pattern on aigate-public; main services internal-only.
  Shared DATA_DIR_ASR_CANARY across CPU + CUDA.
- Resource manager: cuda-stt / cpu-stt split into speaches + canary
  groups for cross-service eviction.
- LiteLLM whisper_transformation monkey-patch keeps parakeet endpoints
  from receiving verbose_json.
- crisper-whisper alias dropped (upstream HF card missing library_name).
- Docs, Makefile, .env.example, tests updated.