feat(TASK-12): periodic telemetry reporter — 15min interval, collector POST

Background task spawned on server startup: every 15 minutes, checks opt-in
status, builds anonymous health report (node ID hash, version, uptime,
CPU/RAM/disk %, container states, recent alerts), saves to disk, and POSTs
to TELEMETRY_COLLECTOR_URL env var if configured. Non-fatal on failure.

Fixed FiredAlert field references (kind not rule_type, timestamp not
fired_at) in both monitoring and analytics modules.

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

core/archipelago/src/api/rpc/analytics.rs

@@ -172,13 +172,12 @@ impl RpcHandler {
             .unwrap_or(0);
 
         // Recent alerts from metrics store
-        let recent_alerts: Vec<serde_json::Value> = self.metrics_store.get_alerts().await
+        let recent_alerts: Vec<serde_json::Value> = self.metrics_store.get_fired_alerts(10).await
             .into_iter()
-            .take(10)
             .map(|a| serde_json::json!({
-                "rule": format!("{:?}", a.rule_type),
+                "rule": format!("{:?}", a.kind),
                 "message": a.message,
-                "fired_at": a.fired_at.to_rfc3339(),
+                "timestamp": a.timestamp,
             }))
             .collect();