PAINTROID-737 Add pipette tool to the colorpicker package

[Amit-Matth]

This PR adds a pipette tool to the color picker, allowing users to pick a color directly from the canvas.

PAINTROID-737

New Features and Enhancements

As present in the native application, a pipette tool for selecting a particular color from the current state of the drawing canvas is implemented. This tool is a part of the colorpicker package itself and allows the user to pick any color from the drawing and use it on other objects.

• Pipette Integration: Added PipetteToolButton to the ColorPicker UI, enabling navigation to the color selection interface.
• Pipette Page: Developed PipettePage to render a screen snapshot and extract colors using ui.Image byte data.
• Precision Loupe: Implemented a magnifying loupe with a crosshair for accurate color picking during pan gestures.
• Confirmation Flow: Added a "Save changes?" dialog to ensure picked colors are not lost when navigating back without confirmation.
• Testing: Created a robust test suite in pipette_button_test.dart covering UI alignment, navigation, color selection, loupe visibility, and dialog interactions.

Refactorings and Bug Fixes

• Refactorings and Bug Fixes

Checklist

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[juliajulie95]

Hi there! Please add the text to the newly merged translation file (or use the already existing ones in there)

[juliajulie95]

Thanks for the changes
I tested it on a Google Pixel 10 and it didn't work like intended. The position was off

PAINTROID-737.mp4

[Amit-Matth]

Thanks for the changes I tested it on a Google Pixel 10 and it didn't work like intended. The position was off

PAINTROID-737.mp4

Thanks for testing! The PR description was actually a bit misleading - the old UI was just a solid color preview, not a real magnifier, which is why aiming with it felt off.

I just pushed a fix to make it a true magnifying glass. It now actually zooms in, and the crosshair perfectly targets the pixel. Give the latest commit a try!

[Amit-Matth]

Also, I noticed the CI failed on the spray_tool_test, but as you can see in the screenshot below, it actually passed perfectly on my fork's CI for the exact same commit. It looks like it was just a random flake with the spray tool test and isn't related to my changes.

Rerunning the failed CI job will clear the error and pass successfully!

[juliajulie95]

Hi! Don't worry about the test, one of our team members is already looking into it

[Amit-Matth]

Hi! Don't worry about the test, one of our team members is already looking into it

Thanks for letting me know!

[juliajulie95]

Works now! Thank you very much!