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/documents/new/+page.svelte

@@ -12,9 +12,8 @@ let { data, form } = $props();
 
 let tags: string[] = $state([]);
 let senderId = $state(untrack(() => data.initialSenderId));
-let selectedReceivers: { id: string; firstName: string; lastName: string }[] = $state(
-	untrack(() => data.initialReceivers)
-);
+let selectedReceivers: { id: string; firstName?: string; lastName: string; displayName: string }[] =
+	$state(untrack(() => data.initialReceivers));
 
 let parsedSuggestion = $state<FilenameParseResult>({});