feat: add appainter icon and update app bar style

[zeshuaro]

No description provided.

[codecov-commenter]

Codecov Report

Merging #261 (bbdd4b9) into main (85d2850) will increase coverage by 0.03%.
The diff coverage is 96.66%.

@@            Coverage Diff             @@
##             main     #261      +/-   ##
==========================================
+ Coverage   97.13%   97.16%   +0.03%     
==========================================
  Files          99       99              
  Lines        3590     3602      +12     
==========================================
+ Hits         3487     3500      +13     
+ Misses        103      102       -1     

Impacted Files	Coverage Δ
lib/home/widgets/github_button.dart	75.00% <0.00%> (ø)
lib/home/views/home_page.dart	91.26% <100.00%> (+1.36%)	⬆️
lib/home/widgets/app_theme_mode_button.dart	100.00% <100.00%> (ø)
lib/home/widgets/export_button.dart	100.00% <100.00%> (ø)
lib/home/widgets/import_button.dart	88.23% <100.00%> (+3.61%)	⬆️
lib/home/widgets/usage_button.dart	95.00% <100.00%> (ø)

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