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.

utils/numberFormatter.ts

@@ -0,0 +1,8 @@
+export const numberFormatter = (num: number, symbol?: string): string => {
+	const formatter = new Intl.NumberFormat("de-DE", {
+		style: "decimal",
+		minimumFractionDigits: 2,
+		maximumFractionDigits: 2
+	});
+	return formatter.format(num) + (symbol ? ` ${symbol}` : "");
+};

utils/randomTailwindColor.ts

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+type TailwindColorPrefix = "text" | "bg" | "shadow" | "from" | "to" | "via" | "group-hover:shadow" | "group-active:shadow";
+
+type TailwindColorShade = 50 | 100 | 150 | 200 | 300 | 400 | 500 | 600 | 700 | 800 | 900;
+
+export const randomTailwindColor = (rand: number, prefix: TailwindColorPrefix = "bg", shade: TailwindColorShade = 100, suffix = "") => {
+	const tailwindColors = [
+		"red",
+		"orange",
+		"amber",
+		"yellow",
+		"lime",
+		"green",
+		"emerald",
+		"teal",
+		"cyan",
+		"sky",
+		"blue",
+		"indigo",
+		"violet",
+		"purple",
+		"fuchsia",
+		"pink",
+		"rose"
+	];
+
+	const randomColorIndex = rand % tailwindColors.length;
+
+	return `${prefix}-${tailwindColors[randomColorIndex]}-${shade}${suffix}`;
+};

utils/scrollProgress.ts

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+export const scrollProgress = () => {
+	if (!import.meta.client) return 0;
+
+	const { documentElement, body } = document;
+	const windowScroll = body.scrollTop || documentElement.scrollTop;
+	const height = documentElement.scrollHeight - documentElement.clientHeight;
+	return height > 0 ? Math.round((windowScroll / height) * 100) : 0;
+};

utils/slugify.ts

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+export function slugify(text: string): string {
+	return text
+		.toLowerCase()
+		.replace(/\s+/g, "-")
+		.replace(/ü/g, "ue")
+		.replace(/ä/g, "ae")
+		.replace(/ö/g, "oe")
+		.replace(/ß/g, "ss");
+}

utils/trackEvent.ts

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+declare global {
+	interface Window {
+		umami?: {
+			track: (event: string, data?: Record<string, unknown>) => void;
+		};
+	}
+}
+
+export const trackEvent = (event: string, data?: Record<string, unknown>) => {
+	if (import.meta.client && window.umami) {
+		window.umami.track(event, data);
+	}
+};