feat: Replace window.confirm() with styled ConfirmDialog component

[JamalMohamedR]

Description

Replaces all window.confirm() usages with a reusable, styled HTML confirmation modal component (ConfirmDialog). The native browser dialog was visually inconsistent with the application's UI and appeared differently across operating systems.

This change introduces a consistent, accessible, and reusable confirmation pattern aligned with the app’s design system.

Fixes #273

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Type of Change

• Bug fix
• New feature
• Breaking change
• Documentation update

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How Has This Been Tested?

Manually verified both trigger points in the browser:

• Clicked New button in the toolbar → custom HTML modal appeared (not browser dialog) → Cancel keeps workspace, Confirm clears it ✅

• Opened Share Pipeline → added code → clicked Load Pipeline with existing blocks → custom modal appeared → Cancel aborts, Confirm loads pipeline ✅

• Existing tests pass

• New tests added

• Manual testing

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Screenshots (if applicable)

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Checklist

• My code follows the project's style guidelines
• I have performed a self-review
• I have added/updated documentation as needed
• My changes generate no new warnings
• Tests pass locally

[ivantha]

Thanks for the PR! It currently has merge conflicts with main (or is behind). Could you rebase onto the latest main and push the updated branch? Happy to merge once it's auto-rebasable.