feat: Snackbar action button with a different background color

[g123k]

Hi everyone!

To improve the readability/accessibility of SnackBar buttons, they now have a background color.
Also, we've received one feedback on Slack: the duration of the SnackBar used on the lists is too short (fixed).

Before/After:

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 10.00000% with 9 lines in your changes missing coverage. Please review.

Project coverage is 6.20%. Comparing base (4d9c7fc) to head (f8162fd).
Report is 674 commits behind head on develop.

Files with missing lines	Patch %	Lines
...h_app/lib/generic_lib/widgets/smooth_snackbar.dart	0.00%	9 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           develop   #6233      +/-   ##
==========================================
- Coverage     9.54%   6.20%   -3.35%     
==========================================
  Files          325     456     +131     
  Lines        16411   26715   +10304     
==========================================
+ Hits          1567    1657      +90     
- Misses       14844   25058   +10214     

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