Prevent CameraPreview toolbar clipping on compact screens

[Vetle444]

Description of Change

Addresses Arena.Mobile #2053.

• Allows custom CameraPreview bottom toolbar content to grow to its natural height while preserving the calculated letterbox height as its minimum.
• Keeps zoom controls and bottom overlay offsets above the toolbar's actual rendered height.
• Adds a compact-screen regression test based on the measured iPhone SE scanner layout.

Todos

• I have tested on an Android device.
• I have tested on an iOS device.
• I have supported accessibility

[Copilot]

Pull request overview

This PR fixes an iOS compact-screen layout issue in CameraPreview where custom bottom toolbar content could be clipped by allowing the bottom toolbar container to grow to its natural height while still reserving the computed letterbox height as a minimum. It also updates zoom/overlay offset calculations to respect the toolbar’s rendered height and adds a regression unit test for the measured iPhone SE layout case.

Changes:

• Update CameraPreview to set a minimum bottom toolbar height (letterbox) instead of a fixed HeightRequest, allowing content-driven growth.
• Ensure zoom control margin and overlay offset calculations use the effective bottom toolbar height.
• Add a compact-screen regression unit test and document the fix in CHANGELOG.md.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 2 comments.

File	Description
src/library/DIPS.Mobile.UI/API/Camera/Preview/CameraPreview.cs	Allows bottom toolbar to expand beyond the letterbox minimum and updates dependent offsets/margins accordingly.
src/tests/unittests/API/Camera/Preview/CameraPreviewTests.cs	Adds a compact-screen regression test based on iPhone SE measurements.
CHANGELOG.md	Adds a patch-note entry describing the CameraPreview clipping fix.