chore(deps): bump koa from 2.15.3 to 2.15.4 in /backend

Bumps [koa](https://github.com/koajs/koa) from 2.15.3 to 2.15.4.
- [Release notes](https://github.com/koajs/koa/releases)
- [Changelog](https://github.com/koajs/koa/blob/2.15.4/History.md)
- [Commits](koajs/koa@2.15.3...2.15.4)

---
updated-dependencies:
- dependency-name: koa
  dependency-type: direct:production
...

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

backend/package.json

@@ -62,7 +62,7 @@
     "jsmodbus": "4.0.10",
     "jsonwebtoken": "9.0.2",
     "knex": "3.1.0",
-    "koa": "2.15.3",
+    "koa": "2.15.4",
     "koa-bodyparser": "4.4.1",
     "koa-helmet": "8.0.1",
     "koa-respond": "2.1.0",