feat: add ClickHouse DataSource and JdbcTemplate configuration

Adds ClickHouseProperties (bound to clickhouse.*), ClickHouseConfig
(conditional HikariDataSource + JdbcTemplate beans), and extends
application.yml with clickhouse.enabled/url/username/password and
cameleer.storage.metrics properties.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

cameleer3-server-app/src/main/resources/application.yml

@@ -48,6 +48,8 @@ opensearch:
 cameleer:
   body-size-limit: ${CAMELEER_BODY_SIZE_LIMIT:16384}
   retention-days: ${CAMELEER_RETENTION_DAYS:30}
+  storage:
+    metrics: ${CAMELEER_STORAGE_METRICS:postgres}
 
 security:
   access-token-expiry-ms: 3600000
@@ -66,6 +68,12 @@ springdoc:
   swagger-ui:
     path: /api/v1/swagger-ui
 
+clickhouse:
+  enabled: ${CLICKHOUSE_ENABLED:false}
+  url: ${CLICKHOUSE_URL:jdbc:clickhouse://localhost:8123/cameleer?async_insert=1&wait_for_async_insert=0}
+  username: ${CLICKHOUSE_USERNAME:default}
+  password: ${CLICKHOUSE_PASSWORD:}
+
 management:
   endpoints:
     web: