config: switch datasource to PostgreSQL, add OpenSearch and Flyway config

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

cameleer3-server-app/src/test/resources/application-test.yml

@@ -1,18 +1,5 @@
 spring:
-  datasource:
-    url: jdbc:ch://placeholder:8123/cameleer3
-    username: default
-    password: ""
-    driver-class-name: com.clickhouse.jdbc.ClickHouseDriver
-
-ingestion:
-  buffer-capacity: 100
-  batch-size: 10
-  flush-interval-ms: 100
-
-agent-registry:
-  ping-interval-ms: 1000
-
-security:
-  bootstrap-token: test-bootstrap-token
-  bootstrap-token-previous: old-bootstrap-token
+  flyway:
+    enabled: true
+opensearch:
+  url: http://localhost:9200