init: hgmj server initial commit

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

common/maths/round.go

@@ -0,0 +1,23 @@
+package maths
+
+import "math"
+
+func Round(input float64, places int) (rounded float64, err error) {
+	if math.IsNaN(input) {
+		return math.NaN(), NaNErr
+	}
+	sign := 1.0
+	if input < 0 {
+		sign = -1
+		input *= -1
+	}
+	precision := math.Pow(10, float64(places))
+	digit := input * precision
+	_, decimal := math.Modf(digit)
+	if decimal >= 0.5 {
+		rounded = math.Ceil(digit)
+	} else {
+		rounded = math.Floor(digit)
+	}
+	return rounded / precision * sign, nil
+}