build(deps-dev): bump @types/node

Bumps the development group in /services/backend with 1 update: [@types/node](https://github.com/DefinitelyTyped/DefinitelyTyped/tree/HEAD/types/node).


Updates `@types/node` from 26.2.0 to 26.3.0
- [Release notes](https://github.com/DefinitelyTyped/DefinitelyTyped/releases)
- [Commits](https://github.com/DefinitelyTyped/DefinitelyTyped/commits/HEAD/types/node)

---
updated-dependencies:
- dependency-name: "@types/node"
  dependency-version: 26.3.0
  dependency-type: direct:development
  update-type: version-update:semver-minor
  dependency-group: development
...

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

services/backend/package.json

@@ -31,7 +31,7 @@
   "devDependencies": {
     "@biomejs/biome": "latest",
     "@types/express": "^5.0.6",
-    "@types/node": "^26.2.0",
+    "@types/node": "^26.3.0",
     "@types/pg": "^8.23.1",
     "@types/ws": "^8.18.1",
     "tsx": "^4.23.12",