deps: bump ethers from 6.15.0 to 6.16.0

Bumps [ethers](https://github.com/ethers-io/ethers.js) from 6.15.0 to 6.16.0.
- [Release notes](https://github.com/ethers-io/ethers.js/releases)
- [Changelog](https://github.com/ethers-io/ethers.js/blob/main/CHANGELOG.md)
- [Commits](ethers-io/ethers.js@v6.15.0...v6.16.0)

---
updated-dependencies:
- dependency-name: ethers
  dependency-version: 6.16.0
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

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

Author: dependabot[bot]

backend/package.json

@@ -21,7 +21,7 @@
     "@ipld/dag-json": "^10.2.5",
     "@sinclair/typebox": "^0.34.41",
     "debug": "^4.4.3",
-    "ethers": "^6.15.0",
+    "ethers": "^6.16.0",
     "index-provider-peer-id": "^1.0.1",
     "lru-cache": "^11.2.4",
     "multiformats": "^13.4.1",