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.

layouts/default.vue

@@ -0,0 +1,39 @@
+<template>
+	<div>
+		<Header :covers="covers" :is-dark-mode="isDarkMode" />
+		<slot />
+		<Footer :covers="covers" />
+		<CookieBanner />
+	</div>
+</template>
+
+<script setup lang="ts">
+import type { CoverNavItem } from "~/types";
+import { slugify } from "~/utils/slugify";
+
+const isDarkMode = ref(false);
+
+// Fetch covers (SSR-safe)
+const { data: coversData } = await useFetch("/api/product-covers", {
+	transform: (response: { data?: Array<{ id: string | number; attributes?: { name: string; binding?: string; sort?: number }; name?: string; binding?: string; sort?: number }> }) =>
+		response.data?.map((cover) => {
+			const name = cover.attributes?.name ?? cover.name ?? "";
+			return {
+				label: name,
+				id: cover.id,
+				slug: slugify(name),
+				description: cover.attributes?.binding ?? cover.binding ?? "",
+				sort: cover.attributes?.sort ?? cover.sort ?? 0
+			};
+		}) ?? []
+});
+
+const covers = computed<CoverNavItem[]>(() => coversData.value ?? []);
+
+function toggleDarkMode(value: boolean) {
+	isDarkMode.value = value;
+}
+
+// Provide to children
+provide("toggleDarkMode", toggleDarkMode);
+</script>