point gateway at remote bee for PSS routing

Local prod_bee can't peer with the Swarm mainnet (bootnode handshake
mismatch — see prior commits pinning 2.7.1). Remote node at
bee.ffaerber.duckdns.org is 2.7.2-rc1 with 25 live peers + usable
stamps, so PSS dispatch works there. Keeping prod_bee in the stack
for now (idle but harmless) so we can swap back once mainnet bootnodes
are usable.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

hostinger/prod-stack.yaml

@@ -56,7 +56,7 @@ services:
       DATABASE_URL: postgresql://hosted:hosted@postgres:5432/hosted_gateway?schema=public
       REDIS_HOST: redis
       REDIS_PORT: 6379
-      BEE_API_URL: http://bee:1633
+      BEE_API_URL: https://bee.ffaerber.duckdns.org
       HOSTED_GATEWAY_PORT: 8080
     networks:
       - public
@@ -95,7 +95,7 @@ services:
       DATABASE_URL: postgresql://hosted:hosted@postgres:5432/hosted_gateway?schema=public
       REDIS_HOST: redis
       REDIS_PORT: 6379
-      BEE_API_URL: http://bee:1633
+      BEE_API_URL: https://bee.ffaerber.duckdns.org
     networks:
       - internal
     deploy: