chore: add system metrics

backend/internal/grpcsrv/collector/collector.go

@@ -157,3 +157,8 @@ func (c *Collector) GetAgent(name string) (*Agent, bool) {
 func (c *Collector) Agents() []*Agent {
 	return c.tracker.Agents()
 }
+
+// GetSystemMetrics delegates to the tracker.
+func (c *Collector) GetSystemMetrics() map[string]AgentMetricsInfo {
+	return c.tracker.GetSystemMetrics()
+}