Data portability / no lock-in (task 1907, export half). GET /api/notes/export streams a zip of the caller's notes: a machine-readable notes.json (notes + labels + items + reminders + attachment refs), a human-readable Markdown file per note (frontmatter + body / checklist), and the attachment media. Sidebar 'Export' link (same-origin GET, session cookie) downloads it. _slugify unit-tested. Import (Google Keep Takeout) is the follow-up increment of this task. Pure backend + small frontend; no migration. Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_01FRgehjoz7Yv8LkUfADxACm