Improve UX, add popover tour, metadata, and hicolor icons

- Redesign tutorial tour from modal dialogs to popovers pointing at actual UI elements
- Add beginner-friendly improvements: help buttons, tooltips, welcome wizard enhancements
- Add AppStream metainfo with screenshots, branding, categories, keywords, provides
- Update desktop file with GTK category and SingleMainWindow
- Add hicolor icon theme with all sizes (16-512px)
- Fix debounce SourceId panic in rename step
- Various step UI improvements and bug fixes

pixstrip-gtk/src/step_indicator.rs

@@ -49,10 +49,24 @@ impl StepIndicator {
         container.append(&grid);
 
         // First step starts as current
+        let total = dots.len();
         if let Some(first) = dots.first() {
             first.icon.set_icon_name(Some("radio-checked-symbolic"));
             first.button.set_sensitive(true);
             first.label.add_css_class("accent");
+            first.button.update_property(&[
+                gtk::accessible::Property::Label(
+                    &format!("Step 1 of {}: {} (current)", total, first.label.label())
+                ),
+            ]);
+        }
+        // Label all non-current dots
+        for (i, dot) in dots.iter().enumerate().skip(1) {
+            dot.button.update_property(&[
+                gtk::accessible::Property::Label(
+                    &format!("Step {} of {}: {}", i + 1, total, dot.label.label())
+                ),
+            ]);
         }
 
         Self {
@@ -164,11 +178,17 @@ impl StepIndicator {
     pub fn set_completed(&self, actual_index: usize) {
         let dots = self.dots.borrow();
         let map = self.step_map.borrow();
+        let total = dots.len();
         if let Some(visual_i) = map.iter().position(|&i| i == actual_index) {
             if let Some(dot) = dots.get(visual_i) {
                 dot.icon.set_icon_name(Some("emblem-ok-symbolic"));
                 dot.button.set_sensitive(true);
                 dot.label.remove_css_class("accent");
+                dot.button.update_property(&[
+                    gtk::accessible::Property::Label(
+                        &format!("Step {} of {}: {} (completed)", visual_i + 1, total, dot.label.label())
+                    ),
+                ]);
             }
         }
     }