fix: pg_isready healthcheck must specify database name

Without -d, pg_isready connects to database matching the username
('cameleer'), which doesn't exist. Specify $POSTGRES_DB explicitly.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

docker-compose.yml

@@ -23,7 +23,7 @@ services:
       - pgdata:/var/lib/postgresql/data
       - ./docker/init-databases.sh:/docker-entrypoint-initdb.d/init-databases.sh:ro
     healthcheck:
-      test: ["CMD-SHELL", "pg_isready -U ${POSTGRES_USER:-cameleer}"]
+      test: ["CMD-SHELL", "pg_isready -U ${POSTGRES_USER:-cameleer} -d ${POSTGRES_DB:-cameleer_saas}"]
       interval: 5s
       timeout: 5s
       retries: 5