chore: fix permissions in Dockerfile for private/pipelines

Dockerfile

@@ -70,7 +70,7 @@ COPY --from=build /rails /rails
 # Run and own only the runtime files as a non-root user for security
 RUN groupadd --system --gid 1000 rails && \
     useradd rails --uid 1000 --gid 1000 --create-home --shell /bin/bash && \
-    chown -R rails:rails db log storage tmp
+    chown -R rails:rails db log storage tmp private private/pipelines
 USER 1000:1000
 
 # Entrypoint prepares the database.