feat(persons): add notes field to person profile (issue #23)

V5 Flyway migration adds TEXT notes column; Person entity, service, and
controller updated to persist notes. Frontend edit form adds textarea and
view mode renders the notes section. Backed by 2 new service unit tests
(persist + blank clears).

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

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

@@ -28,6 +28,7 @@ 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 notes = formData.get('notes')?.toString().trim() || undefined;
 
         if (!firstName || !lastName) {
             return fail(400, { updateError: 'Vor- und Nachname sind Pflichtfelder.' });
@@ -36,7 +37,7 @@ 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 } : {}), ...(notes ? { notes } : {}) }
         });
 
         if (apiError) {