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>

pom.xml

@@ -44,6 +44,13 @@
                 <artifactId>cameleer3-server-core</artifactId>
                 <version>${project.version}</version>
             </dependency>
+            <dependency>
+                <groupId>org.testcontainers</groupId>
+                <artifactId>testcontainers-bom</artifactId>
+                <version>${testcontainers.version}</version>
+                <type>pom</type>
+                <scope>import</scope>
+            </dependency>
         </dependencies>
     </dependencyManagement>