feat(utils): add personFormat utility module with 6 pure functions (TDD)

abbreviateName, formatXsMeta, personAvatarColor (djb2), formatDate,
statusDotClass, statusLabel — 27 tests all green

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

frontend/src/lib/utils/personFormat.ts

@@ -0,0 +1,102 @@
+import { formatDocumentStatus } from './documentStatusLabel';
+
+type Person = { firstName: string; lastName: string };
+type DocumentStatus = 'PLACEHOLDER' | 'UPLOADED' | 'TRANSCRIBED' | 'REVIEWED' | 'ARCHIVED';
+type DocForMeta = {
+	sender?: Person | null;
+	receivers?: Person[];
+	documentDate?: string | null;
+};
+
+const AVATAR_PALETTE = ['#012851', '#5A3080', '#007596', '#2A6040', '#803020'] as const;
+
+function djb2(str: string): number {
+	let hash = 5381;
+	for (let i = 0; i < str.length; i++) {
+		hash = (hash * 33) ^ str.charCodeAt(i);
+	}
+	return Math.abs(hash);
+}
+
+export function abbreviateName(person: Person): string {
+	const first = person.firstName.trim();
+	const last = person.lastName.trim();
+	if (!last) return first;
+	return `${first.charAt(0)}. ${last}`;
+}
+
+function abbreviateCompact(person: Person): string {
+	const first = person.firstName.trim();
+	const last = person.lastName.trim();
+	if (!last) return first;
+	return `${first.charAt(0)}.${last}`;
+}
+
+export function formatXsMeta(doc: DocForMeta): string {
+	const parts: string[] = [];
+
+	const receivers = doc.receivers ?? [];
+	if (doc.sender) {
+		const senderAbbr = abbreviateCompact(doc.sender);
+		if (receivers.length === 0) {
+			parts.push(senderAbbr);
+		} else {
+			const extra = receivers.length - 1;
+			const firstReceiver = abbreviateCompact(receivers[0]);
+			parts.push(
+				extra > 0
+					? `${senderAbbr} → ${firstReceiver} +${extra}`
+					: `${senderAbbr} → ${firstReceiver}`
+			);
+		}
+	} else if (receivers.length > 0) {
+		const extra = receivers.length - 1;
+		const firstReceiver = abbreviateCompact(receivers[0]);
+		parts.push(extra > 0 ? `${firstReceiver} +${extra}` : firstReceiver);
+	}
+
+	if (doc.documentDate) {
+		parts.push(formatDate(doc.documentDate, 'short'));
+	}
+
+	return parts.join(' · ');
+}
+
+export function personAvatarColor(personId: string): string {
+	return AVATAR_PALETTE[djb2(personId) % AVATAR_PALETTE.length];
+}
+
+export function formatDate(isoDate: string, format: 'short' | 'long'): string {
+	const date = new Date(isoDate + 'T12:00:00');
+	if (format === 'short') {
+		return new Intl.DateTimeFormat('de-DE', {
+			day: '2-digit',
+			month: '2-digit',
+			year: 'numeric'
+		}).format(date);
+	}
+	return new Intl.DateTimeFormat('de-DE', {
+		day: 'numeric',
+		month: 'long',
+		year: 'numeric'
+	}).format(date);
+}
+
+export function statusDotClass(status: DocumentStatus): string {
+	switch (status) {
+		case 'PLACEHOLDER':
+			return 'bg-gray-400';
+		case 'UPLOADED':
+			return 'bg-emerald-500';
+		case 'TRANSCRIBED':
+			return 'bg-blue-400';
+		case 'REVIEWED':
+			return 'bg-amber-400';
+		case 'ARCHIVED':
+			return 'bg-emerald-600';
+	}
+}
+
+export function statusLabel(status: string): string {
+	return formatDocumentStatus(status);
+}