Wire skill level and accessibility settings to UI

- Add detailed_mode to AppState, derived from skill_level setting
- Expand advanced option sections by default in Detailed mode
  (resize, convert, compress, watermark steps)
- Fix high contrast to use HighContrast GTK theme
- Add completion sound via canberra-gtk-play

pixstrip-gtk/src/app.rs

@@ -94,6 +94,7 @@ pub struct AppState {
     pub excluded_files: Rc<RefCell<std::collections::HashSet<std::path::PathBuf>>>,
     pub output_dir: Rc<RefCell<Option<std::path::PathBuf>>>,
     pub job_config: Rc<RefCell<JobConfig>>,
+    pub detailed_mode: bool,
 }
 
 #[derive(Clone)]
@@ -218,6 +219,7 @@ fn build_ui(app: &adw::Application) {
         loaded_files: Rc::new(RefCell::new(Vec::new())),
         excluded_files: Rc::new(RefCell::new(std::collections::HashSet::new())),
         output_dir: Rc::new(RefCell::new(None)),
+        detailed_mode: app_cfg.skill_level.is_advanced(),
         job_config: Rc::new(RefCell::new(JobConfig {
             resize_enabled: if remember { sess_state.resize_enabled.unwrap_or(true) } else { true },
             resize_width: if remember { sess_state.resize_width.unwrap_or(1200) } else { 1200 },
@@ -2503,11 +2505,10 @@ fn apply_accessibility_settings() {
     let config = config_store.load().unwrap_or_default();
 
     if config.high_contrast {
-        // Use libadwaita's high contrast mode
-        let style_manager = adw::StyleManager::default();
-        style_manager.set_color_scheme(adw::ColorScheme::ForceLight);
-        // High contrast is best achieved via the GTK_THEME env or system
-        // settings; the app respects system high contrast automatically
+        // Request high contrast by switching to the HighContrast theme.
+        // This works on GNOME systems with the standard HC theme installed.
+        let settings = gtk::Settings::default().unwrap();
+        settings.set_gtk_theme_name(Some("HighContrast"));
     }
 
     let settings = gtk::Settings::default().unwrap();

pixstrip-gtk/src/steps/step_compress.rs

@@ -295,6 +295,7 @@ pub fn build_compress_page(state: &AppState) -> adw::NavigationPage {
     let advanced_expander = adw::ExpanderRow::builder()
         .title("Per-Format Quality")
         .subtitle("Fine-tune quality for each format individually")
+        .expanded(state.detailed_mode)
         .build();
 
     let jpeg_row = adw::SpinRow::builder()

pixstrip-gtk/src/steps/step_convert.rs

@@ -145,6 +145,7 @@ pub fn build_convert_page(state: &AppState) -> adw::NavigationPage {
         .title("Format Mapping")
         .subtitle("Different input formats can convert to different outputs")
         .show_enable_switch(false)
+        .expanded(state.detailed_mode)
         .build();
 
     let progressive_row = adw::SwitchRow::builder()

pixstrip-gtk/src/steps/step_resize.rs

@@ -372,6 +372,7 @@ pub fn build_resize_page(state: &AppState) -> adw::NavigationPage {
         .title("Advanced Options")
         .subtitle("Resize algorithm, DPI, upscale behavior")
         .show_enable_switch(false)
+        .expanded(state.detailed_mode)
         .build();
 
     let upscale_row = adw::SwitchRow::builder()

pixstrip-gtk/src/steps/step_watermark.rs

@@ -176,6 +176,7 @@ pub fn build_watermark_page(state: &AppState) -> adw::NavigationPage {
         .title("Advanced Options")
         .subtitle("Opacity, rotation, tiling, margin")
         .show_enable_switch(false)
+        .expanded(state.detailed_mode)
         .build();
 
     let opacity_row = adw::SpinRow::builder()