fix: refactor ClickHouse config to match cameleer3-server pattern

- Add ClickHouseProperties with @ConfigurationProperties
- @ConditionalOnProperty to toggle ClickHouse
- @Primary DataSource + JdbcTemplate for PostgreSQL (prevents Spring
  Boot from routing JPA/Flyway to ClickHouse)
- HikariDataSource for ClickHouse with explicit credentials
- Remove separate DataSourceConfig.java (merged into ClickHouseConfig)
- Remove database-platform override (no longer needed with @Primary)

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

src/main/resources/application.yml

@@ -54,4 +54,7 @@ cameleer:
     cameleer3-server-endpoint: ${CAMELEER3_SERVER_ENDPOINT:http://cameleer3-server:8081}
     domain: ${DOMAIN:localhost}
   clickhouse:
+    enabled: ${CLICKHOUSE_ENABLED:true}
     url: ${CLICKHOUSE_URL:jdbc:clickhouse://clickhouse:8123/cameleer}
+    username: ${CLICKHOUSE_USERNAME:default}
+    password: ${CLICKHOUSE_PASSWORD:}