fix(elixir): file upload in production

- move uploads to new directory (`./uploads` per default)

Dockerfile

@@ -88,6 +88,10 @@ ENV LC_ALL en_US.UTF-8
 WORKDIR "/app"
 RUN chown nobody /app
 
+# Create data directory for uploads
+RUN mkdir -p /data/uploads/images && \
+    chown -R nobody:root /data/uploads
+
 # set runner ENV
 ENV MIX_ENV="prod"