feat(persons): redesign detail page sections to match Concept A spec

- CoCorrespondentsList: white card wrapper with navy initials circles in chips
- PersonDocumentList: flat row-divider pattern with variant-tinted icons (sent=navy, received=teal)
- Add variant prop (sent/received) to PersonDocumentList and wire up in page
- Add person_correspondents_hint i18n key to all three message files

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

frontend/src/routes/persons/[id]/+page.svelte

@@ -78,12 +78,14 @@ const coCorrespondents = $derived.by(() => {
 				documents={sentDocuments}
 				heading={m.person_docs_heading()}
 				emptyMessage={m.person_no_docs()}
+				variant="sent"
 			/>
 
 			<PersonDocumentList
 				documents={receivedDocuments}
 				heading={m.person_received_docs_heading()}
 				emptyMessage={m.person_no_received_docs()}
+				variant="received"
 			/>
 		</div>
 	</div>