docs(about): state the GeoLite2 licence in full

The credits page named CC BY-SA 4.0 alone. MaxMind stopped distributing
GeoLite2 under that licence by itself: the databases ship under the
GeoLite End User License Agreement, which incorporates CC BY-SA 4.0 by
reference and controls wherever the two disagree. Name both, in that
order, and link the EULA. The attribution string was already there and
is unchanged; the e2e page check now asserts both licences rather than
the one that no longer stands alone.

Reconcile the self-hosting guide with the same wording, point it at the
current EULA URL, and say why the `/about` page must stay reachable — it
is where an operator's own attribution lives.

Correct the project licence line while on the page: it still claimed
AGPL-3.0, which the page's own footer contradicts. The trunk has been
PolyForm Noncommercial 1.0.0 since v1.15.19.

docs/self-hosting/geolite2.md

@@ -100,9 +100,16 @@ not immediately. A weekly `geoipupdate` followed by
 
 The databases are downloaded under your own MaxMind account, so their
 terms are between you and MaxMind — read what your account agrees to at
-<https://www.maxmind.com/en/geolite2/eula>. HealthLog's own attribution
-("this product includes GeoLite2 data created by MaxMind") is already on
-the `/about` page and covers an instance that uses them.
+<https://www.maxmind.com/en/geolite/eula>. That agreement, the GeoLite
+End User License Agreement, incorporates CC BY-SA 4.0 by reference and
+controls wherever the two disagree; both require you to attribute the
+data to MaxMind if you make it available to anyone else.
+
+HealthLog's own attribution ("This product includes GeoLite2 data
+created by MaxMind, available from https://www.maxmind.com") is already
+on the `/about` page and covers an instance that uses them. Keep that
+page reachable — it is what carries the attribution for your deployment,
+and it is served without a session for exactly that reason.
 
 ## Troubleshooting