feat: remove shadowed wrapper

[ChasNelson1990]

Description

This PR does 2 things:

1. it merges all of the .wrapper CSS into one bit - wrappers should be identical across pages so I think this makes sense. This change definitely belongs here.
2. it sets the .main background colour to primary10 (keeping the .homepage .hero as light. This requires a knock-on to make sure that sidebar modules have a background colour of light. I am not 100% sure if this change belongs here or in ZaRR - thoughts @A-Souhei?

relates (but is not dependent on) fjelltopp/ckanext-zarr#44

Checklist

• The Jira ticket for this issue has been updated to "Ready to Review" or equivalent.
• I have developed these changes in discussion with the appropriate project manager.
• My code follows the general Fjelltopp documentation (see Confluence).
• I have made corresponding changes to the Fjelltopp documentation (see Confluence).
• I have rebased this branch with master.
• New dependency changes have been committed.
• I have added automated tests that prove my fix is effective or that my feature works.
• New and existing tests pass locally with my changes.
• My changes generate no new warnings.
• I have performed a self-review of my own code.
• I have assigned at least one reviewer.
• I have assigned at least one label to this PR: "patch", "minor", "major".

[ChasNelson1990]

Not quite sure how this got closed?

[A-Souhei]

@ChasNelson1990 ,
With changing the background we will also need to change the dataset read page, or shall we just keep the dataset read page background white?

I want to think that in ZaRR it could be easier but I am not sure

[ChasNelson1990]

Oh, yes, let's make the dataset read pages white.

Probably all things under the tabs should be white?