Allow doing math in price field for each markups

assets/javascripts/blur.js

@@ -0,0 +1,33 @@
+function evaluateMathExpression(expr) {
+  if (!expr) return null;
+
+  // allow only digits, decimal, operators, parentheses, spaces
+  if (!/^[0-9+\-*/().\s]+$/.test(expr)) {
+    return null;
+  }
+
+  try {
+    return Function('"use strict"; return (' + expr + ')')();
+  } catch {
+    return null;
+  }
+}
+
+document.addEventListener("blur", function(e) {
+
+  if (!e.target.classList.contains("price-field")) return;
+
+  const field = e.target;
+  const value = field.value.trim();
+
+  const result = evaluateMathExpression(value);
+
+  if (result !== null && !isNaN(result)) {
+    field.value = Number(result).toFixed(2);
+  }
+
+  if (typeof updateLineItemTotals === "function") {
+    updateLineItemTotals();
+  }
+
+}, true);