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.

e2e/v1427-public-pages.spec.ts

@@ -41,6 +41,12 @@ test.describe("v1.4.27 — public pages", () => {
     // GeoLite2 attribution is the load-bearing reason this page exists.
     await expect(page.getByText(/GeoLite2/).first()).toBeVisible();
     await expect(page.getByText(/MaxMind/).first()).toBeVisible();
+    // Both licences, because naming only the Creative Commons one understates
+    // the terms: the GeoLite EULA is what governs and CC BY-SA 4.0 rides
+    // inside it.
+    await expect(
+      page.getByText(/GeoLite End User License Agreement/i),
+    ).toBeVisible();
     await expect(page.getByText(/Attribution-ShareAlike 4\.0/i)).toBeVisible();
   });