- Fix attachment URLs to use /api/trips/:id/files/:id/download instead
of /uploads/files/... which was unconditionally blocked with 401
- Use getAuthUrl() with ephemeral tokens for displaying attachments and
opening them in a new tab (images, PDFs, documents)
- Replace htmlFor/id label pattern with ref.current.click() for the
file picker button in NoteFormModal — fixes file not being added to
pending list on first note creation
- Add integration tests COLLAB-028 to COLLAB-031 covering URL format,
listing URLs, ephemeral token download, and unauthenticated 401
