feat(frontend): replace all name concatenation with displayName

- Add displayName default method to PersonSummaryDTO
- Update native SQL queries to include title, person_type columns
- Add getInitials() utility to personFormat.ts
- Update abbreviateName/abbreviateCompact for nullable firstName
- Replace firstName+lastName concatenation with displayName in all
  person-displaying components and server load files
- Regenerate API types with displayName on Person and PersonSummaryDTO

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

frontend/src/routes/persons/[id]/edit/PersonDangerZone.svelte

@@ -6,7 +6,7 @@ let {
 	person,
 	form
 }: {
-	person: { id: string; firstName: string; lastName: string };
+	person: { id: string; firstName?: string | null; lastName: string; displayName: string };
 	form?: { mergeError?: string } | null;
 } = $props();