feat(media): suppress right-click menu on covers/images/videos (friction)
Delegated contextmenu handler that preventDefaults on visual media so the
art isn't one right-click from Save as. Friction only — public files stay
reachable via devtools/network; middle/Ctrl-click (open in new tab) still
works. Text/links/UI keep their normal right-click menu.
- src/views/shell.ejs — document-level contextmenu guard on img/video + cover containers
Co-Authored-By: Claude <noreply@…>