fix(documents): tighten archive/restore idempotency + document fire-and-forget

Three follow-ups from Task 6 code review:
1. applyEntityArchivedSuffix short-circuits when the folder is already
   archived — prevents archivedAt drift on backfill replay.
2. applyEntityRestoredSuffix short-circuits when the folder was never
   archived — matches the docstring's "no-op" claim.
3. Inline comment on archiveClient's fire-and-forget hook documents
   why Task 6 uses void (archive UI doesn't depend on folder sync)
   while Task 5 uses await (rename should be visible to the next
   read).

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

src/lib/services/clients.service.ts

@@ -557,6 +557,10 @@ export async function archiveClient(id: string, portId: string, meta: AuditMeta)
 
   await softDelete(clients, clients.id, id);
 
+  // fire-and-forget: archive UI does not depend on the folder suffix
+  // being stamped before the HTTP response returns. Task 5 (rename
+  // hook) uses await because the rename should be visible to the
+  // next read; archive does not.
   void applyEntityArchivedSuffix(portId, 'client', id).catch((err) => {
     logger.warn({ err, clientId: id }, 'Failed to apply archived suffix to client folder');
   });