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

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

.gitignore

@@ -0,0 +1,39 @@
+# Nuxt dev/build outputs
+.output
+.data
+.nuxt
+.nitro
+.cache
+dist
+
+# Node dependencies
+node_modules
+
+# Logs
+logs
+*.log
+
+# Misc
+.DS_Store
+.fleet
+.idea
+
+# Local env files
+.env
+.env.*
+!.env.example
+
+# libreshop additions
+.env
+.env.local
+.env.*.local
+node_modules/
+.nuxt/
+.output/
+.cache/
+.parcel-cache/
+dist/
+build/
+coverage/
+logs/
+tmp/