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/+page.server.ts

@@ -93,8 +93,8 @@ export async function load({ url, fetch }) {
 			incompleteDocs,
 			recentDocs,
 			initialValues: {
-				senderName: senderObj ? `${senderObj.firstName} ${senderObj.lastName}` : '',
-				receiverName: receiverObj ? `${receiverObj.firstName} ${receiverObj.lastName}` : ''
+				senderName: senderObj?.displayName ?? '',
+				receiverName: receiverObj?.displayName ?? ''
 			},
 			filters: { q, from, to, senderId, receiverId, tags, sort, dir, tagQ },
 			error: null as string | null