feat(persons): add birth/death year fields (issue #18)

V5 Flyway migration adds birth_year and death_year INTEGER columns.
Service validates birthYear <= deathYear (400 otherwise). Frontend edit
form adds year number inputs; view mode renders * year / † year. Backed
by 3 backend service tests and 1 E2E test.

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

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

@@ -28,6 +28,8 @@ export const actions = {
         const firstName = formData.get('firstName')?.toString().trim();
         const lastName = formData.get('lastName')?.toString().trim();
         const alias = formData.get('alias')?.toString().trim() || undefined;
+        const birthYear = formData.get('birthYear')?.toString().trim() || undefined;
+        const deathYear = formData.get('deathYear')?.toString().trim() || undefined;
 
         if (!firstName || !lastName) {
             return fail(400, { updateError: 'Vor- und Nachname sind Pflichtfelder.' });
@@ -36,7 +38,12 @@ export const actions = {
         const api = createApiClient(fetch);
         const { error: apiError } = await api.PUT('/api/persons/{id}', {
             params: { path: { id: params.id } },
-            body: { firstName, lastName, ...(alias ? { alias } : {}) }
+            body: {
+                firstName, lastName,
+                ...(alias ? { alias } : {}),
+                ...(birthYear ? { birthYear } : {}),
+                ...(deathYear ? { deathYear } : {})
+            }
         });
 
         if (apiError) {