* Timeline gets cluttered up with old items over time, and sometimes
  there are several expired short timers before an active long one,
  making it hard to notice it.

  Might be best to split into two lists of active and expired.
  However, that can't be done in the haskell as it stands now; would need
  to be done in the js.

* If two devices are displaying the same page, an add by one is not seen by
  the other one until the page is reloaded.

* Switch to an AJAX display where the js queries the server for a list of
  items and then builds up the display? That would allow solving both
  the cluttered timeline and multi-device update.

  Alternatively, the js could make a long poll to the server, which replies
  when it wants to update the display, and the js then just reloads the
  page. This keeps the js smaller, and it also might replace the hourly
  polling for a changed session id.

* Check if the MediaDevices API is not suported and fall back to file
  upload.
* Expire old images after some reasonable amount of time. This can be done
  with just a find command. Or the js could hide them.
* Add systemd service file and Makefile to install it better.
* Improve CSS. (Patches welcome on this one.)
* The javascript could let things be added in offline mode, and sync up
  with the server next time it comes online. (Patches welcome on this one.)