Fix onnxruntime executable stack error in Docker build

The onnxruntime library requires an executable stack which is blocked
by security restrictions in Docker containers. This adds execstack tool
and uses it to clear the executable stack flag after pip install.

https://claude.ai/code/session_01AGoPJaXqdJnnuxtmSv6NLR

Dockerfile

@@ -22,6 +22,7 @@ FROM python:3.11-slim
 WORKDIR /app
 
 # Install system dependencies for OpenCV, rembg, SAM, and image processing
+# execstack is needed to fix onnxruntime executable stack issue in containers
 RUN apt-get update && apt-get install -y \
     libgl1 \
     libglib2.0-0 \
@@ -31,12 +32,17 @@ RUN apt-get update && apt-get install -y \
     libgomp1 \
     wget \
     git \
+    execstack \
     && rm -rf /var/lib/apt/lists/*
 
 # Copy requirements and install Python dependencies
 COPY backend/requirements.txt .
 RUN pip install --no-cache-dir -r requirements.txt
 
+# Fix onnxruntime executable stack issue in containers
+# This clears the executable stack requirement from the onnxruntime library
+RUN execstack -c /usr/local/lib/python3.11/site-packages/onnxruntime/capi/onnxruntime_pybind11_state.cpython-311-x86_64-linux-gnu.so || true
+
 # Pre-download rembg model (u2net) to avoid first-run delay
 # Note: This downloads the U2-Net model (~170MB) during build
 RUN python -c "from rembg import remove; print('rembg model downloaded')"