fix(qwentts): fix GPU detection race and add ROCm flash-attn support

containers/qwentts/qwentts.Containerfile

@@ -21,7 +21,7 @@ EXPOSE 8000
 # sox (system tool, required at runtime by qwen-tts for audio processing)
 # ffmpeg (optional but commonly needed for reference-audio format conversion)
 RUN apt-get update \
-    && apt-get install -y --no-install-recommends sox ffmpeg curl git \
+    && apt-get install -y --no-install-recommends sox ffmpeg curl git g++ \
     && apt-get autoremove -y \
     && apt-get clean -y \
     && rm -rf /var/lib/apt/lists/*