Replace individual ROCm libs with rocm-libs meta-package; graceful provider fallback

- Dockerfile: rocm-libs installs all ROCm compute libraries at once
  (hipblas, hipfft, hipsparse, rocblas, miopen, etc.) avoiding whack-a-mole
  with individual missing .so files
- engine.py: query ort.get_available_providers() at runtime and only request
  providers that actually loaded — falls back to CPU instead of crashing

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

Dockerfile.rocm

@@ -13,7 +13,7 @@ RUN apt-get update && apt-get install -y --no-install-recommends \
     git \
     ffmpeg \
     libsndfile1 \
-    hipblas \
+    rocm-libs \
     migraphx \
     migraphx-dev \
     half \