feat(stammbaum): centre-on-person control in the panel title row (#692)

Add an onCentre control to StammbaumSidePanel (title row, both desktop aside
and mobile sheet). The page drives a one-shot centreOnId so StammbaumTree
recentres the canvas on the focal node (US-PAN-005). Also tighten the panel
spec's deathYear fixture to a valid type.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

frontend/src/lib/person/genealogy/StammbaumBottomSheet.svelte

@@ -10,9 +10,10 @@ interface Props {
 	node: PersonNodeDTO;
 	canWrite: boolean;
 	onClose: () => void;
+	onCentre?: () => void;
 }
 
-let { node, canWrite, onClose }: Props = $props();
+let { node, canWrite, onClose, onCentre }: Props = $props();
 
 // Swipe the sheet down past this threshold to dismiss it (Leonie).
 const SWIPE_DISMISS_PX = 80;
@@ -70,5 +71,5 @@ function onKeydown(event: KeyboardEvent) {
 		<div class="h-1 w-10 rounded-full bg-line" aria-hidden="true"></div>
 	</div>
 
-	<StammbaumSidePanel node={node} canWrite={canWrite} onClose={onClose} />
+	<StammbaumSidePanel node={node} canWrite={canWrite} onClose={onClose} onCentre={onCentre} />
 </div>

frontend/src/lib/person/genealogy/StammbaumSidePanel.svelte

@@ -14,10 +14,12 @@ type InferredRelationshipWithPersonDTO = components['schemas']['InferredRelation
 interface Props {
 	node: PersonNodeDTO;
 	onClose: () => void;
+	/** When provided, a "centre on this person" control appears in the title row (US-PAN-005). */
+	onCentre?: () => void;
 	canWrite?: boolean;
 }
 
-let { node, onClose, canWrite = false }: Props = $props();
+let { node, onClose, onCentre, canWrite = false }: Props = $props();
 
 let directRels = $state<RelationshipDTO[]>([]);
 let derivedRels = $state<InferredRelationshipWithPersonDTO[]>([]);
@@ -95,23 +97,45 @@ const topDerived = $derived(
 				</p>
 			{/if}
 		</div>
-		<button
-			type="button"
-			onclick={onClose}
-			aria-label={m.comp_dismiss()}
-			class="shrink-0 rounded-sm p-1 text-ink-3 transition hover:bg-muted hover:text-ink focus-visible:ring-2 focus-visible:ring-focus-ring focus-visible:outline-none"
-		>
-			<svg
-				class="h-4 w-4"
-				viewBox="0 0 16 16"
-				fill="none"
-				stroke="currentColor"
-				stroke-width="2"
-				aria-hidden="true"
+		<div class="flex shrink-0 items-center gap-1">
+			{#if onCentre}
+				<button
+					type="button"
+					onclick={onCentre}
+					aria-label={m.stammbaum_centre_on_person()}
+					class="rounded-sm p-1 text-ink-3 transition hover:bg-muted hover:text-ink focus-visible:ring-2 focus-visible:ring-focus-ring focus-visible:outline-none"
+				>
+					<svg
+						class="h-4 w-4"
+						viewBox="0 0 16 16"
+						fill="none"
+						stroke="currentColor"
+						stroke-width="1.5"
+						aria-hidden="true"
+					>
+						<circle cx="8" cy="8" r="2" />
+						<path stroke-linecap="round" d="M8 1v2M8 13v2M1 8h2M13 8h2" />
+					</svg>
+				</button>
+			{/if}
+			<button
+				type="button"
+				onclick={onClose}
+				aria-label={m.comp_dismiss()}
+				class="rounded-sm p-1 text-ink-3 transition hover:bg-muted hover:text-ink focus-visible:ring-2 focus-visible:ring-focus-ring focus-visible:outline-none"
 			>
-				<path stroke-linecap="round" d="M3 3l10 10M13 3L3 13" />
-			</svg>
-		</button>
+				<svg
+					class="h-4 w-4"
+					viewBox="0 0 16 16"
+					fill="none"
+					stroke="currentColor"
+					stroke-width="2"
+					aria-hidden="true"
+				>
+					<path stroke-linecap="round" d="M3 3l10 10M13 3L3 13" />
+				</svg>
+			</button>
+		</div>
 	</div>
 
 	{#if error}

frontend/src/lib/person/genealogy/StammbaumSidePanel.svelte.spec.ts

@@ -11,7 +11,7 @@ const makeNode = () => ({
 	id: 'person-1',
 	displayName: 'Alice Müller',
 	birthYear: 1900,
-	deathYear: null,
+	deathYear: undefined,
 	familyMember: true
 });
 
@@ -50,6 +50,23 @@ describe('StammbaumSidePanel', () => {
 		await expect.element(page.getByText('Alice Müller')).toBeInTheDocument();
 	});
 
+	it('hides the centre control when onCentre is not provided', async () => {
+		render(StammbaumSidePanel, { node: makeNode(), onClose: vi.fn(), canWrite: false });
+		await expect
+			.element(page.getByRole('button', { name: 'Auf diese Person zentrieren' }))
+			.not.toBeInTheDocument();
+	});
+
+	it('calls onCentre when the centre control is clicked (US-PAN-005)', async () => {
+		const onCentre = vi.fn();
+		render(StammbaumSidePanel, { node: makeNode(), onClose: vi.fn(), onCentre, canWrite: false });
+		const btn = [...document.querySelectorAll<HTMLButtonElement>('button')].find(
+			(b) => b.getAttribute('aria-label') === 'Auf diese Person zentrieren'
+		);
+		btn!.click();
+		expect(onCentre).toHaveBeenCalledOnce();
+	});
+
 	it('shows empty-relationships message when no direct relationships are loaded', async () => {
 		render(StammbaumSidePanel, { node: makeNode(), onClose: vi.fn(), canWrite: false });
 		await expect.element(page.getByText('Noch keine Beziehungen bekannt.')).toBeInTheDocument();

frontend/src/routes/stammbaum/+page.svelte

@@ -1,5 +1,5 @@
 <script lang="ts">
-import { untrack } from 'svelte';
+import { untrack, tick } from 'svelte';
 import { m } from '$lib/paraglide/messages.js';
 import { page } from '$app/state';
 import { replaceState } from '$app/navigation';
@@ -42,6 +42,16 @@ function zoomIn() {
 function zoomOut() {
 	view = { ...view, z: clampZoom(view.z - ZOOM_STEP_KB) };
 }
+// One-shot recentre trigger: set the focal id, let StammbaumTree's effect read
+// it and emit the recentred view, then clear so the same person can be
+// re-centred on a later click (US-PAN-005).
+let centreOnId = $state<string | null>(null);
+async function centreOnSelected() {
+	centreOnId = selectedId;
+	await tick();
+	centreOnId = null;
+}
+
 let cancelAnimation = () => {};
 function fitToScreen() {
 	cancelAnimation();
@@ -112,6 +122,7 @@ $effect(() => {
 					edges={data.edges}
 					selectedId={selectedId}
 					panZoom={view}
+					centreOnId={centreOnId}
 					onPanZoom={(v) => (view = v)}
 					onSelect={(id) => (selectedId = id)}
 				/>
@@ -126,6 +137,7 @@ $effect(() => {
 						node={selectedNode}
 						canWrite={canWrite}
 						onClose={() => (selectedId = null)}
+						onCentre={centreOnSelected}
 					/>
 				</aside>
 				<!-- Mobile: dismissible bottom sheet (overlay, preserves pan/zoom) -->
@@ -133,6 +145,7 @@ $effect(() => {
 					node={selectedNode}
 					canWrite={canWrite}
 					onClose={() => (selectedId = null)}
+					onCentre={centreOnSelected}
 				/>
 			{/if}
 		</div>