Upgrade to cashu-ts v4 and drop unused deps.

Adapt amount handling for v4 Amount objects, replace axios/uuid with fetch and crypto.randomUUID, and remove dead helpers.

Co-authored-by: Cursor <cursoragent@cursor.com>

routes/cashu.js

@@ -30,7 +30,7 @@ const cashu = require('../components/cashu');
  *         $ref: '#/components/responses/InternalServerError'
  */
 router.post('/decode', async (req, res) => {
-  const { token } = req.body;
+  const { token } = req.body ?? {};
 
   if (!token) {
     return res.status(400).json({
@@ -48,8 +48,8 @@ router.post('/decode', async (req, res) => {
     }
 
     const decoded = await cashu.parseToken(token);
-    const mintUrl = await cashu.getTokenMintUrl(token);
-    
+    const mintUrl = decoded.mint;
+
     let spent = false;
     try {
       const spendabilityCheck = await cashu.checkTokenSpendable(token);