chore: update docs and config for PostgreSQL/OpenSearch storage layer

- Set failsafe reuseForks=true to reuse JVM across IT classes (faster test suite)
- Replace ClickHouse with PostgreSQL+OpenSearch in docker-compose.yml
- Remove redundant docker-compose.dev.yml
- Update CLAUDE.md and HOWTO.md to reflect new storage stack

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

docker-compose.yml

@@ -1,20 +1,27 @@
 services:
-  clickhouse:
-    image: clickhouse/clickhouse-server:25.3
+  postgres:
+    image: timescale/timescaledb-ha:pg16
     ports:
-      - "8123:8123"
-      - "9000:9000"
-    volumes:
-      - clickhouse-data:/var/lib/clickhouse
-      - ./clickhouse/init:/docker-entrypoint-initdb.d
+      - "5432:5432"
     environment:
-      CLICKHOUSE_USER: cameleer
-      CLICKHOUSE_PASSWORD: cameleer_dev
-      CLICKHOUSE_DB: cameleer3
-    ulimits:
-      nofile:
-        soft: 262144
-        hard: 262144
+      POSTGRES_DB: cameleer3
+      POSTGRES_USER: cameleer
+      POSTGRES_PASSWORD: cameleer_dev
+    volumes:
+      - pgdata:/home/postgres/pgdata/data
+
+  opensearch:
+    image: opensearchproject/opensearch:2.19.0
+    ports:
+      - "9200:9200"
+      - "9300:9300"
+    environment:
+      discovery.type: single-node
+      DISABLE_SECURITY_PLUGIN: "true"
+      OPENSEARCH_JAVA_OPTS: "-Xms512m -Xmx512m"
+    volumes:
+      - osdata:/usr/share/opensearch/data
 
 volumes:
-  clickhouse-data:
+  pgdata:
+  osdata: