refactor: remove all ClickHouse code, old interfaces, and SQL migrations

- Delete all ClickHouse storage implementations and config
- Delete old core interfaces (ExecutionRepository, DiagramRepository, MetricsRepository, SearchEngine, RawExecutionRow)
- Delete ClickHouse SQL migration files
- Delete AbstractClickHouseIT
- Update controllers to use new store interfaces (DiagramStore, ExecutionStore)
- Fix IngestionService calls in controllers for new synchronous API
- Migrate all ITs from AbstractClickHouseIT to AbstractPostgresIT
- Fix count() syntax and remove ClickHouse-specific test assertions
- Update TreeReconstructionTest for new buildTree() method

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

cameleer3-server-app/src/main/java/com/cameleer3/server/app/security/SecurityBeanConfig.java

@@ -16,7 +16,7 @@ import java.util.List;
  * that required security properties are set.
  * <p>
  * Fails fast on startup if {@code CAMELEER_AUTH_TOKEN} is not set.
- * Seeds OIDC config from env vars into ClickHouse if DB is empty.
+ * Seeds OIDC config from env vars into the database if DB is empty.
  */
 @Configuration
 @EnableConfigurationProperties(SecurityProperties.class)