added api logic, vitest, minimal testing ui

web/src/components/CurrencyInput.tsx

@@ -0,0 +1,31 @@
+import React from "react";
+
+export default function CurrencyInput({
+  value,
+  onValue,
+  placeholder = "0.00",
+}: {
+  value: string;
+  onValue: (v: string) => void;
+  placeholder?: string;
+}) {
+  function onChange(e: React.ChangeEvent<HTMLInputElement>) {
+    const raw = e.target.value.replace(/[^0-9.]/g, "");
+    // Keep only first dot, max 2 decimals
+    const parts = raw.split(".");
+    const cleaned =
+      parts.length === 1
+        ? parts[0]
+        : `${parts[0]}.${parts.slice(1).join("").slice(0, 2)}`;
+    onValue(cleaned);
+  }
+  return (
+    <input
+      className="input"
+      inputMode="decimal"
+      placeholder={placeholder}
+      value={value}
+      onChange={onChange}
+    />
+  );
+}