Bump axios from 1.13.5 to 1.15.2 in /backend

Bumps [axios](https://github.com/axios/axios) from 1.13.5 to 1.15.2.
- [Release notes](https://github.com/axios/axios/releases)
- [Changelog](https://github.com/axios/axios/blob/v1.x/CHANGELOG.md)
- [Commits](axios/axios@v1.13.5...v1.15.2)

---
updated-dependencies:
- dependency-name: axios
  dependency-version: 1.15.2
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

Signed-off-by: dependabot[bot] <support@github.com>

Author: dependabot[bot]

backend/package-lock.json

@@ -43,7 +43,7 @@
   "dependencies": {
     "@mempool/electrum-client": "1.1.9",
     "@types/node": "^18.15.3",
-    "axios": "1.13.5",
+    "axios": "1.15.2",
     "bitcoinjs-lib": "~6.1.3",
     "crypto-js": "~4.2.0",
     "express": "~4.22.1",