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/test/java/com/cameleer3/server/app/AbstractPostgresIT.java

@@ -1,6 +1,8 @@
 package com.cameleer3.server.app;
 
+import org.springframework.beans.factory.annotation.Autowired;
 import org.springframework.boot.test.context.SpringBootTest;
+import org.springframework.jdbc.core.JdbcTemplate;
 import org.springframework.test.context.DynamicPropertyRegistry;
 import org.springframework.test.context.DynamicPropertySource;
 import org.testcontainers.containers.PostgreSQLContainer;
@@ -18,6 +20,9 @@ public abstract class AbstractPostgresIT {
                     .withUsername("cameleer")
                     .withPassword("test");
 
+    @Autowired
+    protected JdbcTemplate jdbcTemplate;
+
     @DynamicPropertySource
     static void configureProperties(DynamicPropertyRegistry registry) {
         registry.add("spring.datasource.url", postgres::getJdbcUrl);