Remove custom MIOpen cache path — let MIOpen use its defaults

The named volume overlay was causing SQLite 'unable to open database file'
crashes. MIOpen's default cache location (~/.config/miopen) works reliably
inside the container. The startup warmup repopulates it each run.

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

Dockerfile.rocm

@@ -41,10 +41,8 @@ COPY engine.py config.py wyoming_handler.py wyoming_voices.py main.py ./
 # Default config (can be overridden by volume mount)
 COPY config.yaml .
 
-# Create default directories (miopen_cache must exist before the volume mounts
-# so MIOpen can open its SQLite benchmark database without crashing)
-RUN mkdir -p voices reference_audio hf_cache miopen_cache && \
-    chmod 777 miopen_cache
+# Create default directories
+RUN mkdir -p voices reference_audio hf_cache
 
 EXPOSE 10200