FLS-1473 Build optimisation changes

[nuwan-samarasinghe]

Ticket: https://mhclgdigital.atlassian.net/browse/FLS-1473

Change description

Build & CI cleanup: submodules, dependencies, Docker, caching; upgrade webpack

Summary

This PR streamlines our build pipeline and dependency management, improves Docker image quality and caching, and upgrades the Designer build to webpack 5 to align with @hapi/hapi v21.

What changed

1. Submodules handled at checkout

   • Move submodule fetching out of Docker and into GitHub Actions checkout.
   • All submodules are now downloaded during CI checkout (no git submodule in Docker).

2. Centralized dependency management

   • Removed manual updates for the xGov form builder joi dependency.
   • Dependencies now resolved via the root package.json (consistent across packages).

3. Immutable installs with Yarn

   • Enforce deterministic installs using yarn.lock (e.g., yarn install --frozen-lockfile).
   • Prevents “works on my machine” version drift.

4. Test & SCSS adjustments

   • Minor updates to tests and styles to reflect consolidated dependencies.
   • Trade-off: small refactors, but much simpler dependency graph.

5. .dockerignore added

   • Stop deleting .git inside the Dockerfile—exclude it via .dockerignore instead.
   • Smaller build context and cleaner images.

6. Simplified Dockerfiles

   • Leaner, easier-to-read Dockerfiles with fewer moving parts.

7. Improved Docker layer caching

   • Layer order optimised so unchanged layers are reused.
   • Rebuilds only when inputs change → faster CI and local builds.

8. Designer build: webpack v4 → v5

   • Upgrade to webpack 5 to match @hapi/hapi 21 support.
   • Updated config/plugins where required.

Why this is better

• Faster builds: Better layer caching and smaller contexts.

• Reproducible installs: Lockfile-driven, immutable dependency resolution.

• Simpler pipeline: Less logic inside Docker; more control in CI.

• Modern toolchain: Designer on webpack 5 for current ecosystem compatibility.

• Unit tests and other appropriate tests added or updated

• README and other documentation has been updated / added (if needed)

• Commit messages are meaningful and follow good commit message guidelines (e.g. "FS-XXXX: Add margin to nav items preventing overlapping of logo")

How to test

All e2e should pass

[sonarqubecloud]

Quality Gate passed

Issues
1 New issue
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud