fix(docker): install libgl1 to satisfy OpenCV libGL.so.1

Dockerfile

@@ -2,6 +2,8 @@ FROM python:3.11-slim
 
 # Install system dependencies as root first
 RUN apt-get update && apt-get install -y \
+    # libGL runtime needed by OpenCV when non-headless builds are present
+    libgl1 \
     libgl1-mesa-dri \
     libglib2.0-0 \
     libsm6 \