Allow clearing and replacing auction bids

lib/integer-input.ts

@@ -0,0 +1,6 @@
+// A blank edit is not a zero. Keep input text separate from submitted numbers.
+export function integerInputValue(text: string): number {
+  if (text.trim() === '') return Number.NaN;
+  const value = Number(text);
+  return Number.isSafeInteger(value) ? value : Number.NaN;
+}