Publish ARMv7 multi-arch Docker image

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

deployment/Dockerfile

@@ -22,7 +22,7 @@ ENV PATH="/opt/venv/bin:$PATH"
 COPY requirements.txt /tmp/
 COPY src/ /tmp/src/
 # Prefer prebuilt wheels when available to avoid building larger compiled artifacts
-RUN pip install --no-cache-dir --prefer-binary -r /tmp/requirements.txt
+RUN SODIUM_INSTALL=system python -m pip install --no-cache-dir --prefer-binary -r /tmp/requirements.txt
 
 # Strip compiled extensions and remove tests/pycache in venv to reduce size
 RUN set -eux; \