SFTP UI replicates S3 Admin UI - single PR from main

Slava asked at 2026-06-05T21:53Z (Slack DM thread 1780696408.792149) for the SFTP UI to replicate the S3 Admin UI for both targets list and target details page. He confirmed at 21:57Z he wants ONE PR for this, not the existing 7-PR BOLT-1183 stack (#11739-#11746). The BOLT-1183 stack remains open but unmerged. Approach: cherry-pick the apps/admin SFTP-only changes from the top of that stack (mono-bolt-1190 worktree) onto a fresh branch cato/sftp-s3-parity from origin/main. Files: apps/admin/app/(shell)/data-ingest/sftp/[slug]/page.tsx (rewrite), apps/admin/hooks/useSftpPollTargetFiles.ts (new), apps/admin/hooks/useSftpPollTargetFiles.test.ts (new), and tiny loadingRowCount removals on apps/admin/components/data-ingest/{S3PollList,SftpPollList}.tsx. Skip the graphql.ts diff (codegen drift, unrelated).