deploy: prod uses container-FQDN for DATABASE_URL / REDIS_URL

The shared \`intranet\` Docker network has many other containers
aliased as \`db\` and \`redis\` (mastodon-db, mailman redis, etc.).
Docker's embedded DNS resolved those before our own services, sending
the app's MySQL connection to the wrong IP and crashing it in a restart
loop.

Switched both DATABASE_URL and REDIS_URL in the prod overlay to use
the project-prefixed container names (readmarkets-db-1,
readmarkets-redis-1), which are globally unique on the Docker daemon.
Applied to both app and scheduler.

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

docker-compose.prod.yml

@@ -19,6 +19,24 @@ services:
     networks:
       - default
       - intranet
+    # The shared `intranet` network has many other containers aliased as
+    # `db` and `redis`; Docker's embedded DNS would pick one of those
+    # before ours. Use the project-prefixed container names instead —
+    # those are globally unique on the daemon.
+    environment:
+      DATABASE_URL: mysql+aiomysql://${MARIADB_USER:-cassandra}:${MARIADB_PASSWORD:-changeme}@readmarkets-db-1:3306/${MARIADB_DATABASE:-cassandra}
+      REDIS_URL: redis://readmarkets-redis-1:6379/0
+
+  scheduler:
+    # Scheduler isn't fronted by NPM, so it doesn't need intranet — but
+    # it does share the same DNS-collision problem on `default` (it only
+    # joins `default`, where our `db` alias would normally win… except
+    # the scheduler too is multi-network if you ever decide to expose
+    # its health endpoint via NPM). Future-proofing: use the explicit
+    # container names here too.
+    environment:
+      DATABASE_URL: mysql+aiomysql://${MARIADB_USER:-cassandra}:${MARIADB_PASSWORD:-changeme}@readmarkets-db-1:3306/${MARIADB_DATABASE:-cassandra}
+      REDIS_URL: redis://readmarkets-redis-1:6379/0
 
 networks:
   intranet: