feat(designer): dismissable barrier warnings

[johannesvedder]

This pull request introduces several improvements to the form handling and sidesheet modal logic, especially around unsaved changes and form dirty state detection. The changes enhance user experience by providing better prompts for unsaved changes, improving form state management, and making the modal sidesheet more flexible.

Form Dirty State Handling and Modal Dismissal:

• Improved dirty state detection in FormViewModel by introducing a more reliable way to compare the initial and current form state, using a new _getFullFormValue() method and a dedicated finalizeInitializationBaseline() function. This ensures that programmatic changes to the form do not incorrectly mark it as dirty. [1] [2] [3] [4]
• Added a new _FormSidesheetPopEntry widget and integrated it into the form sidesheet flow. This widget intercepts the modal pop action and, if the form is dirty, prompts the user with an UnsavedChangesDialog. If the user confirms, the form cancels and the modal is dismissed; otherwise, the modal remains open. [1] [2] [3]
• Changed the default for barrierDismissible in showFormSideSheet to true, allowing users to dismiss the modal by clicking outside it, but with proper handling of unsaved changes.

Sidesheet Modal Enhancements:

• Updated showModalSideSheet to accept a new wrapRoute parameter, allowing the modal content to be wrapped with custom widgets (such as _FormSidesheetPopEntry for pop interception). [1] [2] [3]

Minor Improvements:

• Simplified the DismissButton in form_buttons.dart to directly pop the navigation stack, removing unnecessary async logic.
• Updated the Supabase public anon key in the development environment configuration.
• Ensured prevFormValue is initialized in InviteCodeFormViewModel for correct dirty state tracking.

[github-actions]

Visit the preview URL for this PR (updated for commit 35141f1):

• https://studyu-dev-app--pr803-feat-dismissable-bar-jlt0xtqy.web.app
• https://studyu-dev-designer--pr803-feat-dismissable-bar-oag99ekp.web.app

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[mohiuddinshahrukh]

Thanks for the PR.

AFter running it locally, I think this needs changes before merge because the main unsaved-changes protection can be bypassed in a common path.

Change

When editing a survey question sidesheet, I changed the question title and clicked the sidesheet Cancel button while the text field was still focused. The sidesheet closed immediately without showing the unsaved-changes dialog, and the edit was discarded.

The console showed:

[PopEntry] _handleDismiss isDirty=false```