feature: Show progress bar across screens in "add new rule" user flow

[suvanl]

Summary of the feature

Display a linear progress bar to convey how much the user has progressed in the "add new rule" flow (currently FmlScreen.SelectRuleType and FmlScreen.AddRule).

Rationale behind the feature request

To improve UX by allowing users (particularly first-time users) to understand how long this flow takes to complete, and how much progress they have currently made.

Describe a possible solution

Share the progress state (e.g., a value between 0F and 1F) across screens and use this to set the level of progress on the progress bar.

Definition of done

• The progress bar is visible regardless of layout size class
• Progress bar completion state updates as user progresses through screens
  • Could have:
    • completing form fields also furthers the progress level
    • if the form field is emptied, progress gets rolled back.
• All related tests pass

Additional information

No response