fix(build): Use a pre-created user for the frontend image

[khvn26]

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Changes

This fixes the following user-reported error when running the frontend container:

Error: failed to create containerd container: mount callback failed on /var/lib/containerd/tmpmounts/containerd-mount675064683: no users found

An alternative solution would be to add a RUN useradd node layer to the target stage.

How did you test this code?

The user in question tested the PR image on their premises and reported success.

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3 Skipped Deployments

Name	Status	Preview	Comments	Updated (UTC)
docs	⬜️ Ignored (Inspect)			Jul 25, 2024 5:51pm
flagsmith-frontend-preview	⬜️ Ignored (Inspect)			Jul 25, 2024 5:51pm
flagsmith-frontend-staging	⬜️ Ignored (Inspect)			Jul 25, 2024 5:51pm

[github-actions]

Docker builds report

Image	Build Status	Security report
ghcr.io/flagsmith/flagsmith-api-test:pr-4394	Finished ✅	Skipped
ghcr.io/flagsmith/flagsmith-e2e:pr-4394	Finished ✅	Skipped
ghcr.io/flagsmith/flagsmith-frontend:pr-4394	Finished ✅	Results ✅
ghcr.io/flagsmith/flagsmith-api:pr-4394	Finished ✅	Results ✅
ghcr.io/flagsmith/flagsmith:pr-4394	Finished ✅	Results ✅
ghcr.io/flagsmith/flagsmith-private-cloud:pr-4394	Finished ✅	Results ✅

[github-actions]

Uffizzi Preview deployment-54657 was deleted.