Add procps to Docker for pkill command

Fixes error on window close when stopping docs server.

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Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

Dockerfile

@@ -11,6 +11,7 @@ FROM python:3.12-slim
 # Install system dependencies for Qt GUI
 RUN apt-get update && apt-get install -y --no-install-recommends \
     git \
+    procps \
     libgl1 \
     libegl1 \
     libxkbcommon0 \