[Bug]: [Dashboard] Refund form default amount incorrectly rounds sub-cent pending_difference using toFixed

[damienNiji]

Package.json file

{
  "name": "example",
  "version": "0.0.62",
  "description": "",
  "scripts": {
    "build": "medusa build",    
    "dev": "medusa develop",    
  },
  "dependencies": {
    "@aws-sdk/client-dynamodb": "^3.0.0",
    "@medusajs/admin-sdk": "2.13.1",
    "@medusajs/auth": "2.13.1",
    "@medusajs/auth-emailpass": "2.13.1",
    "@medusajs/auth-google": "2.13.1",
    "@medusajs/caching-redis": "^2.13.4",
    "@medusajs/cli": "2.13.1",
    "@medusajs/draft-order": "2.13.1",
    "@medusajs/framework": "2.13.1",
    "@medusajs/index": "2.13.1",
    "@medusajs/medusa": "2.13.1",
    "ajv": "^8.17.1",
    "ajv-formats": "^3.0.1",
    "algoliasearch": "5.39.0",
    "cronstrue": "^3.12.0",
    "dayjs": "^1.11.18",
    "fast-xml-parser": "^5.5.6",
    "json-rules-engine": "^7.3.1",
    "jsonwebtoken": "^9.0.2",
    "nodemailer": "^7.0.11"
  },
  "devDependencies": {
    "@biomejs/biome": "2.0.6",
    "@medusajs/test-utils": "2.13.1",
    "@swc/core": "1.5.7",
    "@swc/jest": "0.2.39",
    "@types/ajv": "^0.0.5",
    "@types/jest": "30.0.0",
    "@types/jsonwebtoken": "^9.0.10",
    "@types/node": "^22.0.0",
    "@types/nodemailer": "^7.0.4",
    "@types/react": "^18.3.2",
    "@types/react-dom": "^18.2.25",
    "jest": "30.2.0",
    "react": "^18.2.0",
    "react-dom": "^18.2.0",
    "ts-node": "^10.9.2",
    "typescript": "5.9.3",
    "vite": "^5.4.21",
    "yalc": "^1.0.0-pre.53"
  },  
  "engines": {
    "node": ">=24.1.0"
  },
  "volta": {
    "node": "24.1.0",
    "yarn": "4.12.0"
  },
  "overrides": {
    "axios": "1.13.5",
    "glob": "11.1.0",
    "immutable": "4.3.8",
    "jws": "4.0.1",
    "multer": "2.1.1",
    "qs": "6.14.1",
    "rollup": "4.59.0",
    "tar": "7.5.11",
    "@isaacs/brace-expansion": "5.0.1",
    "fast-xml-parser": "5.5.6",
    "minimatch@^10.1.1": "10.2.3"
  },
  "resolutions": {
    "tar": "7.5.11",
    "@isaacs/brace-expansion": "5.0.1",
    "fast-xml-parser": "5.5.6",
    "axios": "1.13.5",
    "immutable": "4.3.8",
    "multer": "2.1.1",
    "rollup": "4.59.0",
    "minimatch@^10.1.1": "10.2.3"
  },
  "packageManager": "yarn@4.12.0"
}

Node.js version

24.1.0

Database and its version

PostGres 16-alpine

Operating system name and version

MAC Docker

Browser name

Chrome

What happended?

Description

When an order has a pending_difference with sub-cent precision (e.g. -17.705),
the refund form dialog is pre-filled with a different value than the "Refund X€"
button label on the order page.

Steps to reproduce

1. Create an order with a discount that produces sub-cent arithmetic
   (e.g. total = 36.425, pending_difference = -17.705)
2. Request a return for some items
3. On the order page, the "Refund" button shows 17.71€
4. Click it → the refund dialog pre-fills with 17.70€

Root cause

In create-refund-form.tsx:

form.setValue("amount", {
  value: normalizedAmount.toFixed(currency.decimal_digits), // BUG
  float: normalizedAmount,
})

### Expected behavior


// Use (decimal-aware via the shortest string representation):
const str = normalizedAmount.toString()
const dot = str.indexOf('.')
const dec = dot === -1 ? 0 : str.length - dot - 1
const rounded = dec <= currency.decimal_digits
  ? normalizedAmount
  : Math.round(Math.round(normalizedAmount * 10**dec) / 10**(dec - currency.decimal_digits)) / 10**currency.decimal_digits
value: rounded.toFixed(currency.decimal_digits)

### Actual behavior

value: normalizedAmount.toFixed(currency.decimal_digits)

### Link to reproduction repo

norepo