[Feature][0.12.0-Beta] Enhance Load Average Display, Charting & Alert Grouping (#960)

* Add 1m load

* update alart dialog

* fix null data

* Remove omit zero

* change table and alert view

beszel/internal/alerts/alerts.go

@@ -47,6 +47,7 @@ type SystemAlertStats struct {
 	NetSent      float64            `json:"ns"`
 	NetRecv      float64            `json:"nr"`
 	Temperatures map[string]float32 `json:"t"`
+	LoadAvg1     float64            `json:"l1"`
 	LoadAvg5     float64            `json:"l5"`
 	LoadAvg15    float64            `json:"l15"`
 }