Switch to ONNX runtime with chatterbox-turbo-ONNX (fp16)

Replaces the PyTorch/chatterbox-tts stack with direct ONNX inference
using ResembleAI/chatterbox-turbo-ONNX fp16 weights.

- engine.py: full rewrite — ONNX sessions, autoregressive KV-cache LM
  loop, voice conditionals cache via speech_encoder outputs
- wyoming_handler.py: remove torch dep, use np.asarray for audio bytes
- requirements-rocm-init.txt: onnxruntime-rocm replaces torch wheels
- requirements-rocm.txt: drop chatterbox/torch deps, keep audio utils
- Dockerfile.rocm: remove chatterbox-tts install step

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

requirements-rocm-init.txt

@@ -1,5 +1 @@
---index-url https://download.pytorch.org/whl/rocm6.1
-torch==2.5.1
-torchaudio==2.5.1
-torchvision==0.20.1
-pytorch_triton_rocm==3.1.0
+onnxruntime-rocm