chore(backend): bump @types/nodemailer in /services/backend

Bumps [@types/nodemailer](https://github.com/DefinitelyTyped/DefinitelyTyped/tree/HEAD/types/nodemailer) from 7.0.11 to 8.0.0.
- [Release notes](https://github.com/DefinitelyTyped/DefinitelyTyped/releases)
- [Commits](https://github.com/DefinitelyTyped/DefinitelyTyped/commits/HEAD/types/nodemailer)

---
updated-dependencies:
- dependency-name: "@types/nodemailer"
  dependency-version: 8.0.0
  dependency-type: direct:development
  update-type: version-update:semver-major
...

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

Author: dependabot[bot]

services/backend/package.json

@@ -58,7 +58,7 @@
     "@release-it/conventional-changelog": "^10.0.5",
     "@types/fs-extra": "^11.0.4",
     "@types/jest": "^30.0.0",
-    "@types/nodemailer": "^7.0.10",
+    "@types/nodemailer": "^8.0.0",
     "@types/pg": "^8.16.0",
     "@types/pug": "^2.0.10",
     "@types/sanitize-html": "^2.16.0",