Bump node from 20.2.0-alpine3.17 to 20.3.0-alpine3.17 in /backend

Bumps node from 20.2.0-alpine3.17 to 20.3.0-alpine3.17.

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

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

backend/Dockerfile

@@ -1,7 +1,7 @@
 ##################################################################################
 # BASE (Is pushed to DockerHub for rebranding) ###################################
 ##################################################################################
-FROM node:20.2.0-alpine3.17 as base
+FROM node:20.3.0-alpine3.17 as base
 
 # ENVs
 ## DOCKER_WORKDIR would be a classical ARG, but that is not multi layer persistent - shame