fix: Edit page: fix regressions after migration to Material 3

[g123k]

Hi everyone,

Here are a few fixes for the Edit product page:

• The background color in light mode is light brown
• All icons are black in light mode

In general and not specific to this page, the weirdo effect of changing the AppBar color when scrolling is removed.

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 66.66667% with 3 lines in your changes missing coverage. Please review.

Project coverage is 7.05%. Comparing base (4d9c7fc) to head (73f8f83).
Report is 422 commits behind head on develop.

Files with missing lines	Patch %	Lines
...mooth_app/lib/pages/product/edit_product_page.dart	0.00%	2 Missing ⚠️
...ackages/smooth_app/lib/widgets/smooth_app_bar.dart	85.71%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           develop   #5781      +/-   ##
==========================================
- Coverage     9.54%   7.05%   -2.50%     
==========================================
  Files          325     411      +86     
  Lines        16411   22236    +5825     
==========================================
+ Hits          1567    1569       +2     
- Misses       14844   20667    +5823     

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[teolemon]

thank you @g123k