components: memoize and streamline callbacks

src/components/SizeInput/SizeInput.tsx

@@ -7,11 +7,12 @@ import "./SizeInput.css";
 type SizeInputProps = {};
 
 const handleFocus = (event: React.UIEvent<HTMLInputElement>) => {
-  const { currentTarget } = event;
-  currentTarget.focus();
+  event.preventDefault();
+  event.currentTarget.focus();
 };
 
 const handleBlur = (event: React.UIEvent<HTMLInputElement>) => {
+  event.preventDefault();
   event.currentTarget.blur();
 };