add signal strength indicator dot to all systems table

internal/site/src/lib/wifi.ts

@@ -1,3 +1,4 @@
+import { MeterState } from "@/lib/enums"
 import type { SystemRecord, WiFi } from "@/types"
 
 // Current system info is independent of the selected historical chart window.
@@ -21,6 +22,11 @@ export function strongestWiFiSignal(system: Pick<SystemRecord, "status" | "info"
 	return strongestWiFi(connectedWiFi(system))?.[1].r
 }
 
+/** Signal quality for an RSSI reading: good at -65 dBm or stronger, warn down to -75 dBm, crit below. */
+export function wifiSignalState(rssi: number): MeterState {
+	return rssi >= -65 ? MeterState.Good : rssi >= -75 ? MeterState.Warn : MeterState.Crit
+}
+
 export function wifiColor(id: string): string {
 	let hash = 0
 	for (const char of id) hash = (Math.imul(hash, 31) + char.charCodeAt(0)) | 0