No signal on site.

-- migration 0022: a reply lost after commit became a retry, and the retry duplicated
alter table activities add column if not exists client_key text;
create unique index if not exists uq_activities_client_key
  on activities (client_key) where client_key is not null;

// excerpt from sync.ts, shortened
export const MAX_SYNC_ATTEMPTS = 5;

export async function syncPending() {
  if (running) return;           // concurrency lock
  if (!navigator.onLine) return;
  running = true;
  try {
    for (const item of await listUnsynced()) {
      if (!navigator.onLine) break;
      if (item.attempts >= MAX_SYNC_ATTEMPTS) continue; // waits for manual retry
      try { await syncOne(item); }
      catch (e) {
        await patchActivity(item.localId, {
          status: 'error',
          error: e instanceof Error ? e.message : 'Falha ao sincronizar',
          attempts: item.attempts + 1,
        });
      }
    }
  } finally { running = false; }
}