fix(stammbaum): drop inferred relationships that are already direct

A spouse listed as a direct PersonRelationship was also being
emitted as an inferred SPOUSE chip below, so the same person
appeared twice in the Beziehungen card.

Filter the inferred list against the IDs already shown as direct
edges before slicing the top 5. Added a component test that
renders red without the filter and green with it.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

frontend/src/routes/persons/[id]/PersonRelationshipsCard.svelte

@@ -14,7 +14,10 @@ interface Props {
 
 let { personId, relationships, inferredRelationships }: Props = $props();
 
-const topDerived = $derived(inferredRelationships.slice(0, 5));
+const directOtherIds = $derived(new Set(relationships.map((rel) => otherId(rel))));
+const topDerived = $derived(
+	inferredRelationships.filter((d) => !directOtherIds.has(d.person.id)).slice(0, 5)
+);
 
 function chipLabel(rel: RelationshipDTO): string {
 	const viewpointIsSubject = rel.personId === personId;