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/lib/components/PersonMultiSelect.svelte

@@ -73,8 +73,7 @@ function removePerson(id: string | undefined) {
 			<span
 				class="inline-flex items-center gap-1 rounded bg-muted px-2 py-1 text-sm font-medium text-ink"
 			>
-				{person.firstName}
-				{person.lastName}
+				{person.displayName}
 				<button
 					type="button"
 					onclick={() => removePerson(person.id)}
@@ -121,7 +120,7 @@ function removePerson(id: string | undefined) {
 						role="button"
 						tabindex="0"
 					>
-						{person.lastName}, {person.firstName}
+						{person.displayName}
 					</div>
 				{/each}
 			{/if}