feat: extract nginx from mp/nginx — initial libreshop/nginx

Source moved verbatim from mp/nginx/ on 2026-04-29; mp was the first
concrete adapter consuming the libreshop toolkit. Builds and publishes
git.librete.ch/libreshop/nginx on every main / v* push via the standard
.gitea/workflows/build.yml shared across libreshop components.

Dockerfile

@@ -0,0 +1,9 @@
+# Libre Shop - (Reverse) Proxy
+# Version 1.0.0
+
+FROM nginx:1.26.2
+
+COPY docker-entrypoint.sh /docker-entrypoint.sh
+RUN chmod +x /docker-entrypoint.sh
+
+CMD ["/docker-entrypoint.sh"]