Show file and comment visibility clearly: Class Files note + Admin only info icon

Context: Featurebase #448 (Miranda Harvey, 16 Oct 2026). She wasn't sure whether students could see completed class paperwork uploaded to Class Files, which includes other students' results. They can't; only trainers and admins can, and only Resources are shared with students. Nothing in the UI says so.

1. Class Files: add a calm info line above the upload/drop area: "Class files are only visible to trainers and admins. Students can't see them. To share a file with students, add it as a Resource." Check this matches sharingScope behaviour from RTOP-695 before writing it. (Keep this always-visible — privacy stakes are high; an (i) alone is too easy to miss here.)
2. Comments: in apps/rto-pilot-ui/components/forms/comment/CreateCommentForm.tsx (~L340–361), the "Admin only" checkbox only has a hover tooltip, which touch users never see. Do not put helper text underneath. Add a small (i) info icon next to the "Admin only" checkbox; clicking or tapping it shows: "Admin only: hidden from trainers. Students never see comments." so it works on touch devices as well as desktop. First check in the backend that students genuinely can't see comments, and adjust the wording if they can.
3. Make sure the CommentCard/CommentFilesView "Admin only" badge wording is consistent.

Acceptance: shots at 1440 and 375, the copy is accurate against the backend, no behaviour change. Info popover/tooltip must work on tap (375) as well as hover (1440).