Add setup wizard sidebar with completed-step indicators

[astrovm]

Motivation

• Improve the setup wizard UX by providing a persistent sidebar that shows all steps and indicates which steps are complete so users can see progress and navigate the flow more clearly.

Description

• Add a wizard-step-complete CSS rule to style completed step icons and include it in data/resources/style.css.
• Restructure the setup page UI in data/resources/ui/setup_page.ui to introduce a horizontal wizard_box with a left steps_list GtkListBox inside a GtkScrolledWindow and a right content_area_box that holds the existing step_title, step_description, and content_box.
• Extend src/ui/setup_page.rs to track completed steps with a HashSet<&'static str>, expose new template children (steps_list and content_area_box), and add refresh_step_sidebar to render the step list with completion checks and current-step styling.
• Mark the current step as completed in advance_step, ensure show_current_step updates the sidebar and content alignment, and use common::is_step_complete combined with the local completed set to determine completion status.

Testing

• Built the project with cargo build and the build completed successfully.
• Ran the test suite with cargo test and all automated tests passed.

---

Codex Task