fix: add ClickHouse password authentication

ClickHouse default user had no password, causing auth failures on recent
CH versions. Set password via from_env in clickhouse-users.xml, pass
credentials in JDBC URLs to SaaS services and tenant server containers.

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

.env.example

@@ -9,6 +9,9 @@ POSTGRES_USER=cameleer
 POSTGRES_PASSWORD=change_me_in_production
 POSTGRES_DB=cameleer_saas
 
+# ClickHouse
+CLICKHOUSE_PASSWORD=change_me_in_production
+
 # Public domain (used by Traefik, Logto, and SaaS provisioning)
 PUBLIC_HOST=localhost
 PUBLIC_PROTOCOL=https