Attach a photo or video from the composer: the app uploads it to
Litterbox (litterbox.catbox.moe, anonymous, 24 h expiry) and sends only
the link over the mesh. Received photo/video links are previewed inline;
tapping opens them full screen (tap again to return), videos play with
Media3 ExoPlayer on Android.

- When the media can't be loaded (no internet, expired link) the plain
  link is shown instead; tapping it opens a compatible app (gallery,
  video player) or the browser.
- A report action on every preview opens a prefilled abuse e-mail to the
  host (admin@catbox.moe), falling back to its contact page.
- New "Photo and video links" setting (default on) turns previews and
  the attach button off; its summary explains that uploads are public
  for 24 h and that loading previews reveals the IP to the host.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>