Initial UI mock for scriptv2 onboarding

[ukutaht]

Changes

• Adds a new scriptv2 feature flag
• When scriptv2 feature flag is enabled, we redirect user from /:domain/installation to /:domain/installationv2 where new installation screen lives for the time being (to be revisited when ready to launch)
• New installation screen separates 'optional measurements' and 'advanced options'. Advanced options is collapsed by default.
• Currently only for manual installation method, will look at switching between installation methods (including new NPM method) in a follow-up PR
• No concern for different flows at the moment, currently only for provisioning flow. Not sure what will happen to "domain changed" flow and "review" flow on this screen
• Missing tests at the moment because the main point is to have something tangible in the UI but it's very much subject to change during the course of the project.
• Doesn't actually do anything - the script config is not saved anywhere.
• Currently the whole thing is very unfinished but the point is having a UI mock to make progress on the project. Needs many more touches before ready to be used for real

It's nowhere near production-ready and needs lots of extra work. Whether to keep this on a branch or keep merging the WIP is up for discussion.

Screen.Recording.2025-05-07.at.16.31.17.mov

[macobo]

You asked for a quick review - this seems like a decent starting point!