fix: UI changes for the homepage

[g123k]

Hi everyone!

Here are a few changes to the homepage:

• The scanner is now edge-to-edge
• There is a slight background color below the status bar
• Now that the scanner is below the appbar, the carousel will be a little taller
• The content of the tagline is fully clickable
• The indicator of the tagline is white (same as in #5895)
• The arrow in the button is circled

Generally speaking, we can now assume that the tagline body can have up to 3 lines on all configs.

And a screenshot: (cc @stephanegigandet)

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 0% with 58 lines in your changes missing coverage. Please review.

Project coverage is 6.64%. Comparing base (4d9c7fc) to head (1d70b50). Report is 500 commits behind head on develop.

Files with missing lines	Patch %	Lines
...ib/pages/scan/carousel/main_card/scan_tagline.dart	0.00%	32 Missing :warning:
packages/smooth_app/lib/pages/scan/scan_page.dart	0.00%	22 Missing :warning:
...es/smooth_app/lib/pages/scan/camera_scan_page.dart	0.00%	4 Missing :warning:

Additional details and impacted files

```diff @@ Coverage Diff @@ ## develop #5911 +/- ## ========================================== - Coverage 9.54% 6.64% -2.91% ========================================== Files 325 435 +110 Lines 16411 24401 +7990 ========================================== + Hits 1567 1622 +55 - Misses 14844 22779 +7935 ```

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