Pin base image to rocm/dev-ubuntu-22.04:7.2, restore torch 2.11.0

Using :latest was pulling a ROCm 6.x image whose MIOpen was incompatible
with our ROCm 7.2 PyTorch wheels. Pinning to the 7.2 tag gives matching
MIOpen libraries and should resolve the workspace/fallback performance issue.

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

Dockerfile.rocm

@@ -1,4 +1,4 @@
-FROM rocm/dev-ubuntu-22.04:latest
+FROM rocm/dev-ubuntu-22.04:7.2
 
 ENV DEBIAN_FRONTEND=noninteractive \
     PYTHONDONTWRITEBYTECODE=1 \

requirements-rocm-init.txt

@@ -1,3 +1,3 @@
---index-url https://download.pytorch.org/whl/rocm6.1
+--index-url https://download.pytorch.org/whl/rocm7.2
-torch==2.5.1
+torch==2.11.0
-torchaudio==2.5.1
+torchaudio==2.11.0