Add UX enhancements: carousel, filter chips, command palette, and more

- Replace featured section Stack with AdwCarousel + indicator dots
- Convert category grid to horizontal scrollable filter chips
- Add grid/list view toggle for catalog with compact row layout
- Add quick launch button on library list rows
- Add stale catalog banner when data is older than 7 days
- Add command palette (Ctrl+K) for quick app search and launch
- Show specific app names in update notifications
- Add per-app auto-update toggle (skip updates switch)
- Add keyboard shortcut hints to button tooltips
- Add source trust badges (AppImageHub/Community) on catalog tiles
- Add undo-based uninstall with toast and record restoration
- Add type-to-search in library view
- Use human-readable catalog source labels
- Show Launch button for installed apps in catalog detail
- Replace external browser link with inline AppImage explainer dialog

src/ui/updates_view.rs

@@ -25,7 +25,7 @@ pub fn build_updates_view(db: &Rc<Database>) -> adw::ToolbarView {
     // Check Now button
     let check_btn = gtk::Button::builder()
         .icon_name("view-refresh-symbolic")
-        .tooltip_text(&i18n("Check for updates"))
+        .tooltip_text(&i18n("Check for updates (Ctrl+U)"))
         .build();
     header.pack_end(&check_btn);
 
@@ -86,6 +86,18 @@ pub fn build_updates_view(db: &Rc<Database>) -> adw::ToolbarView {
         .build();
     updates_content.append(&last_checked_label);
 
+    // "What will happen" explanation
+    let explanation = gtk::Label::builder()
+        .label(&i18n("Each app will be downloaded fresh. Your settings and data are kept. You can choose to keep old versions as backup in Preferences."))
+        .css_classes(["caption", "dim-label"])
+        .wrap(true)
+        .xalign(0.0)
+        .margin_start(18)
+        .margin_end(18)
+        .margin_top(6)
+        .build();
+    updates_content.append(&explanation);
+
     let clamp = adw::Clamp::builder()
         .maximum_size(800)
         .tightening_threshold(600)
@@ -255,10 +267,15 @@ fn populate_update_list(state: &Rc<UpdatesState>) {
             .activatable(false)
             .build();
 
-        // Show version info: current -> latest
+        // Show version info: current -> latest (with size if available)
         let current = record.app_version.as_deref().unwrap_or("unknown");
         let latest = record.latest_version.as_deref().unwrap_or("unknown");
-        row.set_subtitle(&format!("{} -> {}", current, latest));
+        let subtitle = if record.size_bytes > 0 {
+            format!("{} -> {} ({})", current, latest, widgets::format_size(record.size_bytes))
+        } else {
+            format!("{} -> {}", current, latest)
+        };
+        row.set_subtitle(&subtitle);
 
         // App icon
         let icon = widgets::app_icon(record.icon_path.as_deref(), name, 32);