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.

components/Heading.vue

@@ -0,0 +1,36 @@
+<script setup lang="ts">
+type Level = 1 | 2 | 3 | 4 | 5;
+type HtmlTag = "h1" | "h2" | "h3" | "h4" | "h5" | "p";
+
+const levelClasses: Record<Level, string> = {
+	1: "text-3xl lg:text-3xl font-bold mb-5 mt-6",
+	2: "text-2xl font-bold mb-4 mt-5",
+	3: "text-xl mt-2 font-semibold mb-1",
+	4: "text-md mt-2 mb-1 font-semibold",
+	5: "text-sm uppercase mb-1 font-semibold mt-2 text-gray-500"
+};
+
+const props = withDefaults(
+	defineProps<{
+		level?: Level;
+		htmlTag?: HtmlTag;
+		classes?: string;
+	}>(),
+	{
+		level: 1,
+		htmlTag: "p",
+		classes: ""
+	}
+);
+
+const computedClass = computed(() => levelClasses[props.level] + " " + props.classes);
+</script>
+
+<template>
+	<h1 v-if="htmlTag === 'h1'" :class="computedClass"><slot /></h1>
+	<h2 v-else-if="htmlTag === 'h2'" :class="computedClass"><slot /></h2>
+	<h3 v-else-if="htmlTag === 'h3'" :class="computedClass"><slot /></h3>
+	<h4 v-else-if="htmlTag === 'h4'" :class="computedClass"><slot /></h4>
+	<h5 v-else-if="htmlTag === 'h5'" :class="computedClass"><slot /></h5>
+	<p v-else :class="computedClass"><slot /></p>
+</template>