update project structure

- move agent to /agent
- change /beszel to /src
- update workflows and docker builds

agent/sensors_default.go

@@ -0,0 +1,9 @@
+//go:build !windows
+
+package agent
+
+import (
+	"github.com/shirou/gopsutil/v4/sensors"
+)
+
+var getSensorTemps = sensors.TemperaturesWithContext