fix: reset seed color when theme brightness updated

[zeshuaro]

Close #342

[codecov-commenter]

Codecov Report

Merging #345 (4e78a5b) into main (9c86551) will increase coverage by 0.00%.
The diff coverage is 80.00%.

@@           Coverage Diff           @@
##             main     #345   +/-   ##
=======================================
  Coverage   97.31%   97.31%           
=======================================
  Files         104      104           
  Lines        3915     3916    +1     
=======================================
+ Hits         3810     3811    +1     
  Misses        105      105           

Impacted Files	Coverage Δ
lib/basic_theme/cubit/basic_theme_cubit.dart	98.33% <80.00%> (+0.01%)	⬆️

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