refactor(stammbaum): use shared chipLabel/otherName from relationshipLabels in both components

Addresses @felix blocker: removes the verbatim duplicate switch+2-line helper
from StammbaumCard.svelte and StammbaumSidePanel.svelte; both now import from
the shared $lib/relationshipLabels helper.

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

frontend/src/lib/components/StammbaumSidePanel.svelte

@@ -2,7 +2,7 @@
 import { onMount } from 'svelte';
 import { invalidateAll } from '$app/navigation';
 import { m } from '$lib/paraglide/messages.js';
-import { inferredRelationshipLabel } from '$lib/relationshipLabels';
+import { chipLabel, otherName, inferredRelationshipLabel } from '$lib/relationshipLabels';
 import PersonTypeahead from '$lib/components/PersonTypeahead.svelte';
 import type { components } from '$lib/generated/api';
 
@@ -120,34 +120,6 @@ async function submitAdd(event: Event) {
 	}
 }
 
-function chipLabel(rel: RelationshipDTO): string {
-	const viewpointIsSubject = rel.personId === node.id;
-	switch (rel.relationType) {
-		case 'PARENT_OF':
-			return viewpointIsSubject ? m.relation_parent_of() : m.relation_child_of();
-		case 'SPOUSE_OF':
-			return m.relation_spouse_of();
-		case 'SIBLING_OF':
-			return m.relation_sibling_of();
-		case 'FRIEND':
-			return m.relation_friend();
-		case 'COLLEAGUE':
-			return m.relation_colleague();
-		case 'EMPLOYER':
-			return m.relation_employer();
-		case 'DOCTOR':
-			return m.relation_doctor();
-		case 'NEIGHBOR':
-			return m.relation_neighbor();
-		default:
-			return m.relation_other();
-	}
-}
-
-function otherName(rel: RelationshipDTO): string {
-	return rel.personId === node.id ? rel.relatedPersonDisplayName : rel.personDisplayName;
-}
-
 function handleEscape(event: KeyboardEvent) {
 	if (event.key === 'Escape') onClose();
 }
@@ -194,10 +166,10 @@ const topDerived = $derived(
 							<span
 								class="inline-flex shrink-0 items-center rounded-full border border-accent/40 bg-accent/15 px-2 py-0.5 font-sans text-xs font-bold tracking-widest text-ink uppercase"
 							>
-								{chipLabel(rel)}
+								{chipLabel(rel, node.id)}
 							</span>
 							<span class="min-w-0 flex-1 truncate font-serif text-xs text-ink">
-								{otherName(rel)}
+								{otherName(rel, node.id)}
 							</span>
 						</li>
 					{/each}