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>

.claude/rules/app-classes.md

@@ -129,6 +129,8 @@ Env-scoped read-path controllers (`AlertController`, `AlertRuleController`, `Ale
 ## metrics/ — Prometheus observability
 
 - `ServerMetrics` — centralized business metrics: gauges (agents by state, SSE connections, buffer depths), counters (ingestion drops, agent transitions, deployment outcomes, auth failures), timers (flush duration, deployment duration). Exposed via `/api/v1/prometheus`.
+- `ServerInstanceIdConfig` — `@Configuration`, exposes `@Bean("serverInstanceId") String`. Resolution precedence: `cameleer.server.instance-id` property → `HOSTNAME` env → `InetAddress.getLocalHost()` → random UUID. Fixed at boot; rotates across restarts so counters restart cleanly.
+- `ServerMetricsSnapshotScheduler` — `@Scheduled(fixedDelayString = "${cameleer.server.self-metrics.interval-ms:60000}")`. Walks `MeterRegistry.getMeters()` each tick, emits one `ServerMetricSample` per `Measurement` (Timer/DistributionSummary produce multiple rows per meter — one per Micrometer `Statistic`). Skips non-finite values; logs and swallows store failures. Disabled via `cameleer.server.self-metrics.enabled=false` (`@ConditionalOnProperty`). Write-only — no query endpoint yet; inspect via `/api/v1/admin/clickhouse/query`.
 
 ## storage/ — PostgreSQL repositories (JdbcTemplate)
 
@@ -145,6 +147,7 @@ Env-scoped read-path controllers (`AlertController`, `AlertRuleController`, `Ale
 - `ClickHouseDiagramStore`, `ClickHouseAgentEventRepository`
 - `ClickHouseUsageTracker` — usage_events for billing
 - `ClickHouseRouteCatalogStore` — persistent route catalog with first_seen cache, warm-loaded on startup
+- `ClickHouseServerMetricsStore` — periodic dumps of the server's own Micrometer registry into the `server_metrics` table. Tenant-stamped (bound at the scheduler, not the bean); no `environment` column (server straddles envs). Batch-insert via `JdbcTemplate.batchUpdate` with `Map(String, String)` tag binding. Written by `ServerMetricsSnapshotScheduler`, query via `/api/v1/admin/clickhouse/query` (no dedicated endpoint yet).
 
 ## search/ — ClickHouse search and log stores