fix: allow ClickHouse connections from Docker network

The default ClickHouse image restricts the 'default' user to localhost
only. Override with clickhouse-users.xml to allow connections from any
IP (needed for inter-container communication on the Docker network).

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

docker-compose.yml

@@ -120,6 +120,7 @@ services:
     volumes:
       - chdata:/var/lib/clickhouse
       - ./docker/clickhouse-init.sql:/docker-entrypoint-initdb.d/init.sql:ro
+      - ./docker/clickhouse-users.xml:/etc/clickhouse-server/users.d/default-user.xml:ro
     healthcheck:
       test: ["CMD-SHELL", "clickhouse-client --query 'SELECT 1'"]
       interval: 10s