Ensure the default environment is always dev

[MuhammadMullah]

Description

This PR sets the default environment to dev when creating a new sandbox

Closes #3954

Validation steps

1. From the menu, Click on Sandboxes
2. Click on the "Create Sandbox" button to create a new sandbox
3. Enter sandbox name and choose preffered color from the pallette
4. Click "Create Sandbox" button to save the sandbox. Note the sandbox will be created with a default environment of dev

To update the environment

From the sidebar menu, click on setting and head to the Project Setup section to update the environemnt

Screen.Recording.2025-12-20.at.05.51.45.mov

Additional notes for the reviewer

None

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• Code generation (copilot but not intellisense)
• Learning or fact checking
• Strategy / design
• Optimisation / refactoring
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• Other
• I have not used AI

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Pre-submission checklist

• I have performed a self-review of my code.
• I have implemented and tested all related authorization policies. (e.g., :owner, :admin, :editor, :viewer)
• I have updated the changelog.
• I have ticked a box in "AI usage" in this PR

[josephjclark]

This looks fantastic @MuhammadMullah , thank you!

Sorry for the late response - a lot of us have been away for a couple of weeks. I'll see about getting this merged.