chore: CI fixes (release-please, renovate, dockerfiles) #455

Job	Run time
prepare-gubbins-frontend-as-a-standalone	2m 44s
prepare-gubbins-backend	2m 1s
run-lint	1m 27s
build-gubbins-dev-image	2m 44s
run-demo	22m 46s
	31m 42s

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