bingo: serve bingo.asxp.io too, credit asxp.io in footer

datacenterbingo.xyz is not in the .xyz zone yet, while bingo.asxp.io
already resolves. Serve the card on both (BINGO_ALT_HOST) so it is
reachable now; canonical and hreflang links keep pointing at the .xyz
domain. Footer gets a copyright line linking back to asxp.io.

Assisted-by: Claude:opus-5

.forgejo/workflows/deploy.yaml

@@ -140,6 +140,7 @@ jobs:
             LTC_ADDRESS=${LTC_ADDRESS}
             CRYPTO_ADDRESSES=${CRYPTO_ADDRESSES}
             BINGO_HOST=datacenterbingo.xyz
+            BINGO_ALT_HOST=bingo.asxp.io
             EOF
             chmod 600 /opt/asxpio/.env