Fix unit conversion logic

src/lib/units.ts

@@ -204,4 +204,22 @@ export function getMetricUnit(unit: string): string {
     default:
       return unit;
   }
+}
+
+// Get display unit based on unit type and measurement system
+export function getDisplayUnit(metricUnit: string, system: MeasurementSystem): string {
+  const unitType = detectUnitType(metricUnit);
+  
+  switch (unitType) {
+    case 'speed':
+      return system === 'imperial' ? 'mph' : 'km/h';
+    case 'distance':
+      return system === 'imperial' ? 'ft' : 'm';
+    case 'height':
+      return system === 'imperial' ? 'in' : 'cm';
+    case 'weight':
+      return system === 'imperial' ? 'lbs' : 'kg';
+    default:
+      return metricUnit;
+  }
 }