feat(stammbaum): person edit Stammbaum & Beziehungen card

New StammbaumCard rendered below the Namensverlauf card on
/persons/{id}/edit:
- Header with "Als Familienmitglied" toggle (form action
  toggleFamilyMember → PATCH /api/persons/{id}/family-member).
- "Erscheint im Stammbaum" banner with deep-link to
  /stammbaum?focus={id} when familyMember is true.
- Direct relationships list grouped by type, then year. Chip text is
  direction-aware: storage subject reads "Elternteil von", storage
  object reads "Kind von" (new relation_child_of i18n key in all 3
  locales). Symmetric and non-family types use their own keys.
- + Beziehung hinzufügen reveals an inline form with type select
  (grouped Familie / Sozial), a PersonTypeahead with the new
  excludePersonId prop (self-rel prevention, Elicit blocker 1), and
  Von / Bis year fields.
- Year validation lives client-side via $derived: empty/empty is OK,
  Bis < Von shows a red text-red-700 error wired with aria-describedby
  and disables submit (Sara blocker 3).
- Self-rel inline error mirrors the typeahead exclusion in case the
  user submits the personId regardless.
- Abgeleitete Beziehungen section (top 5) collapsed by default.

+page.server.ts loads relationships + inferred relationships in the
existing parallel fetch and adds three actions: toggleFamilyMember,
addRelationship (with year-range guard), deleteRelationship.

Refs #358.

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

frontend/src/routes/persons/[id]/edit/+page.server.ts

@@ -17,9 +17,11 @@ export async function load({ params, fetch, locals }) {
 
 	const { id } = params;
 	const api = createApiClient(fetch);
-	const [result, aliasesResult] = await Promise.all([
+	const [result, aliasesResult, relsResult, inferredResult] = await Promise.all([
 		api.GET('/api/persons/{id}', { params: { path: { id } } }),
-		api.GET('/api/persons/{id}/aliases', { params: { path: { id } } })
+		api.GET('/api/persons/{id}/aliases', { params: { path: { id } } }),
+		api.GET('/api/persons/{id}/relationships', { params: { path: { id } } }),
+		api.GET('/api/persons/{id}/inferred-relationships', { params: { path: { id } } })
 	]);
 
 	if (!result.response.ok) {
@@ -29,7 +31,12 @@ export async function load({ params, fetch, locals }) {
 
 	const person = result.data!;
 	const personType = normalizePersonType(person.personType);
-	return { person: { ...person, personType }, aliases: aliasesResult.data ?? [] };
+	return {
+		person: { ...person, personType },
+		aliases: aliasesResult.data ?? [],
+		relationships: relsResult.data ?? [],
+		inferredRelationships: inferredResult.data ?? []
+	};
 }
 
 export const actions = {
@@ -146,5 +153,86 @@ export const actions = {
 		}
 
 		return { aliasSuccess: true };
+	},
+
+	toggleFamilyMember: async ({ request, params, fetch }) => {
+		const formData = await request.formData();
+		const value = formData.get('familyMember')?.toString() === 'true';
+
+		const api = createApiClient(fetch);
+		const result = await api.PATCH('/api/persons/{id}/family-member', {
+			params: { path: { id: params.id } },
+			body: { familyMember: value }
+		});
+
+		if (!result.response.ok) {
+			const code = (result.error as unknown as { code?: string })?.code;
+			return fail(result.response.status, { relationshipError: getErrorMessage(code) });
+		}
+		return { relationshipSuccess: true };
+	},
+
+	addRelationship: async ({ request, params, fetch }) => {
+		const formData = await request.formData();
+		const relatedPersonId = formData.get('relatedPersonId')?.toString();
+		const relationType = formData.get('relationType')?.toString();
+		const fromYearRaw = formData.get('fromYear')?.toString().trim();
+		const toYearRaw = formData.get('toYear')?.toString().trim();
+		const notes = formData.get('notes')?.toString().trim() || undefined;
+
+		if (!relatedPersonId || !relationType) {
+			return fail(400, { relationshipError: getErrorMessage('VALIDATION_ERROR') });
+		}
+		if (relatedPersonId === params.id) {
+			return fail(400, { relationshipError: getErrorMessage('VALIDATION_ERROR') });
+		}
+		const fromYear = fromYearRaw ? parseInt(fromYearRaw, 10) : undefined;
+		const toYear = toYearRaw ? parseInt(toYearRaw, 10) : undefined;
+		if (
+			fromYear !== undefined &&
+			toYear !== undefined &&
+			!Number.isNaN(fromYear) &&
+			!Number.isNaN(toYear) &&
+			toYear < fromYear
+		) {
+			return fail(400, { relationshipError: getErrorMessage('VALIDATION_ERROR') });
+		}
+
+		const api = createApiClient(fetch);
+		const result = await api.POST('/api/persons/{id}/relationships', {
+			params: { path: { id: params.id } },
+			body: {
+				relatedPersonId,
+				relationType,
+				...(fromYear !== undefined && !Number.isNaN(fromYear) ? { fromYear } : {}),
+				...(toYear !== undefined && !Number.isNaN(toYear) ? { toYear } : {}),
+				...(notes ? { notes } : {})
+			}
+		});
+
+		if (!result.response.ok) {
+			const code = (result.error as unknown as { code?: string })?.code;
+			return fail(result.response.status, { relationshipError: getErrorMessage(code) });
+		}
+		return { relationshipSuccess: true };
+	},
+
+	deleteRelationship: async ({ request, params, fetch }) => {
+		const formData = await request.formData();
+		const relId = formData.get('relId')?.toString();
+		if (!relId) {
+			return fail(400, { relationshipError: getErrorMessage('VALIDATION_ERROR') });
+		}
+
+		const api = createApiClient(fetch);
+		const result = await api.DELETE('/api/persons/{id}/relationships/{relId}', {
+			params: { path: { id: params.id, relId } }
+		});
+
+		if (!result.response.ok) {
+			const code = (result.error as unknown as { code?: string })?.code;
+			return fail(result.response.status, { relationshipError: getErrorMessage(code) });
+		}
+		return { relationshipSuccess: true };
 	}
 };

frontend/src/routes/persons/[id]/edit/+page.svelte

@@ -6,6 +6,7 @@ import PersonEditForm from './PersonEditForm.svelte';
 import PersonEditSaveBar from './PersonEditSaveBar.svelte';
 import NameHistoryEditCard from './NameHistoryEditCard.svelte';
 import PersonMergePanel from '../PersonMergePanel.svelte';
+import StammbaumCard from '$lib/components/StammbaumCard.svelte';
 
 let { data, form } = $props();
 const person = $derived(data.person);
@@ -35,6 +36,15 @@ const person = $derived(data.person);
 
 	<NameHistoryEditCard aliases={data.aliases} canWrite={true} aliasError={form?.aliasError} />
 
+	<StammbaumCard
+		personId={person.id}
+		familyMember={person.familyMember ?? false}
+		relationships={data.relationships}
+		inferredRelationships={data.inferredRelationships}
+		canWrite={true}
+		relationshipError={form?.relationshipError}
+	/>
+
 	{#key person.id}
 		<PersonMergePanel person={person} form={form} />
 	{/key}