Add 10 minute refresh to all pages

Since each page displays content that changes with time, add a meta
refresh tag to keep numbers and stats semi-recent.

Use the query string '?auto' for the URL, to distinguish "actual" page
loads from automated page loads in the logs.
Use query string to differentiate stat page reload

Instead of reloading directly, use '?auto-stats' to allow automatic
reloads to be distinguished from "normal" stats queries.
Redirect to stats after payout

Adapt the stats refresh code to redirect from payout to stats
after 10 seconds. Use the '?auto-payout' query string to identify
this event.
Add doge.png background

Use The_pun_fart's dogelogo3.png from the doge_asset repo on GitHub as a
background.
Tweak background image interactions

- Scale background to fit, but don't enlarge the image
- Make menu buttons opaque for visibility