bingo: store photos in their own bucket

The bingo photos sat under bingo/ in the invoice bucket. Store them in
BINGO_S3_BUCKET (datacenterbingo-photos in prod, created and pre-filled
by the storage repo with the same keys) and fall back to S3_BUCKET when
unset, so dev and tests need nothing new.

Assisted-by: Claude:opus-5

.forgejo/workflows/deploy.yaml

@@ -141,6 +141,7 @@ jobs:
             LTC_ADDRESS=${LTC_ADDRESS}
             CRYPTO_ADDRESSES=${CRYPTO_ADDRESSES}
             BINGO_HOST=datacenterbingo.xyz
+            BINGO_S3_BUCKET=datacenterbingo-photos
             INDEXNOW_KEY=${INDEXNOW}
             EOF
             chmod 600 /opt/asxpio/.env