feat(server): persist server self-metrics into ClickHouse

Snapshot the full Micrometer registry (cameleer business metrics, alerting
metrics, and Spring Boot Actuator defaults) every 60s into a new
server_metrics table so server health survives restarts without an external
Prometheus. Includes a dashboard-builder reference for the SaaS team.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

cameleer-server-app/src/main/resources/application.yml

@@ -112,6 +112,10 @@ cameleer:
       url: ${CAMELEER_SERVER_CLICKHOUSE_URL:jdbc:clickhouse://localhost:8123/cameleer}
       username: ${CAMELEER_SERVER_CLICKHOUSE_USERNAME:default}
       password: ${CAMELEER_SERVER_CLICKHOUSE_PASSWORD:}
+    self-metrics:
+      enabled: ${CAMELEER_SERVER_SELFMETRICS_ENABLED:true}
+      interval-ms: ${CAMELEER_SERVER_SELFMETRICS_INTERVALMS:60000}
+    instance-id: ${CAMELEER_SERVER_INSTANCE_ID:}
 
 springdoc:
   api-docs: