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.

README.md

@@ -0,0 +1,25 @@
+# libreshop/nginx
+
+Reverse-proxy template fronting libreshop adapters.
+
+Part of the [libreshop](https://git.librete.ch/libreshop) toolkit. Image
+published at `git.librete.ch/libreshop/nginx` on every push to `main`
+and on `v*` tags.
+
+## Source
+
+This repo was extracted from `mp/nginx/` on 2026-04-29; mp was the
+first concrete adapter consuming the toolkit. mp's `compose.yml` now
+pulls `git.librete.ch/libreshop/nginx:<pin>` instead of building locally.
+
+## Build locally
+
+```
+docker build -t libreshop/nginx:dev .
+```
+
+## Adapter contract
+
+See `docker-entrypoint.sh` and `Dockerfile` for the runtime surface.
+Adapters configure the component via env vars and bind-mounted volumes;
+do not patch the running container or rely on internal paths.