Switch from node-sass to sass

[Steve-Mcl]

Description

• Remove deprecated node-sass
• Install sass
• Update webpack config to mute warnings
• Test thoroughly on pre-staging
• Check / ensure it works with Node 20 and 22

Epic/Story

No response

Have you provided an initial effort estimate for this issue?

I have provided an initial effort estimate

[Steve-Mcl]

FWIW:

I have been rocking sass in place of node-sass locally for ~1 week (multiple stop/start/recompile/lots of front end areas visited & touched - all without any visible issue) (e2e tests may reveal more!)