Ensure the theme is insta-loaded from local storage

[tmeasday]

Issue: Theme was not loading from local storage, leading to a FOUC

What I did

Read the correct key off local storage and preference persisted options to the defauls

How to test

Set theme: themes.dark and reload the SB

[vercel]

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[codecov]

Codecov Report

Merging #5856 into tech/improve-theme-creating will not change coverage.
The diff coverage is 0%.

@@                     Coverage Diff                      @@
##           tech/improve-theme-creating    #5856   +/-   ##
============================================================
  Coverage                        34.99%   34.99%           
============================================================
  Files                              648      648           
  Lines                             9478     9478           
  Branches                          1332     1332           
============================================================
  Hits                              3317     3317           
  Misses                            5533     5533           
  Partials                           628      628

Impacted Files	Coverage Δ
lib/ui/src/core/layout.js	13.79% <0%> (ø)	⬆️

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[shilman]

LGTM