Fix second audit findings and restore crash detection dialog

Address 29 issues found in comprehensive API/spec audit:
- Fix .desktop Exec key path escaping per Desktop Entry spec
- Fix update dialog double-dispatch with connect_response
- Fix version comparison total ordering with lexicographic fallback
- Use RETURNING id for reliable upsert in database
- Replace tilde-based path fallbacks with proper XDG helpers
- Fix backup create/restore path asymmetry for non-home paths
- HTML-escape severity class in security reports
- Use AppStream <custom> element instead of <metadata>
- Fix has_appimage_update_tool to check .is_ok() not .success()
- Use ListBoxRow instead of ActionRow::set_child in ExpanderRow
- Add ELF magic validation to architecture detection
- Add timeout to extract_update_info_runtime
- Skip symlinks in dir_size calculation
- Use Condvar instead of busy-wait in analysis thread pool
- Restore crash detection to single blocking call architecture

src/ui/detail_view.rs

@@ -24,7 +24,7 @@ pub fn build_detail_page(record: &AppImageRecord, db: &Rc<Database>) -> adw::Nav
     // Toast overlay for copy actions
     let toast_overlay = adw::ToastOverlay::new();
 
-    // ViewStack for tabbed content with crossfade transitions.
+    // ViewStack for tabbed content (transitions disabled for instant switching).
     // vhomogeneous=false so the stack sizes to the visible child only,
     // preventing shorter tabs from having excess scrollable empty space.
     let view_stack = adw::ViewStack::new();
@@ -124,10 +124,10 @@ pub fn build_detail_page(record: &AppImageRecord, db: &Rc<Database>) -> adw::Nav
 
             btn_ref.set_sensitive(true);
             match result {
-                Ok(launcher::LaunchResult::Started { child, method }) => {
-                    let pid = child.id();
+                Ok(launcher::LaunchResult::Started { pid, method }) => {
                     log::info!("Launched: {} (PID: {}, method: {})", path, pid, method.as_str());
 
+                    // App survived startup - do Wayland analysis after a delay
                     let db_wayland = db_launch.clone();
                     let path_clone = path.clone();
                     glib::spawn_future_local(async move {
@@ -488,12 +488,7 @@ fn build_overview_tab(record: &AppImageRecord, db: &Rc<Database>) -> gtk::Box {
                     spinner_ref.set_visible(false);
                     if let Ok(Some(data)) = result {
                         let gbytes = glib::Bytes::from(&data);
-                        let stream = gio::MemoryInputStream::from_bytes(&gbytes);
-                        if let Ok(pixbuf) = gtk::gdk_pixbuf::Pixbuf::from_stream(
-                            &stream,
-                            None::<&gio::Cancellable>,
-                        ) {
-                            let texture = gtk::gdk::Texture::for_pixbuf(&pixbuf);
+                        if let Ok(texture) = gtk::gdk::Texture::from_bytes(&gbytes) {
                             picture_ref.set_paintable(Some(&texture));
                             if let Some(slot) = textures_load.borrow_mut().get_mut(idx) {
                                 *slot = Some(texture);
@@ -708,8 +703,11 @@ fn build_overview_tab(record: &AppImageRecord, db: &Rc<Database>) -> gtk::Box {
                             .margin_start(12)
                             .margin_end(12)
                             .build();
-                        let label_row = adw::ActionRow::new();
-                        label_row.set_child(Some(&label));
+                        let label_row = gtk::ListBoxRow::builder()
+                            .activatable(false)
+                            .selectable(false)
+                            .child(&label)
+                            .build();
                         row.add_row(&label_row);
 
                         release_group.add(&row);
@@ -2080,12 +2078,7 @@ fn fetch_favicon_async(url: &str, image: &gtk::Image) {
 
         if let Ok(Some(data)) = result {
             let gbytes = glib::Bytes::from(&data);
-            let stream = gio::MemoryInputStream::from_bytes(&gbytes);
-            if let Ok(pixbuf) = gtk::gdk_pixbuf::Pixbuf::from_stream(
-                &stream,
-                None::<&gio::Cancellable>,
-            ) {
-                let texture = gtk::gdk::Texture::for_pixbuf(&pixbuf);
+            if let Ok(texture) = gtk::gdk::Texture::from_bytes(&gbytes) {
                 image_ref.set_paintable(Some(&texture));
             }
         }

src/ui/update_dialog.rs

@@ -90,17 +90,15 @@ pub fn show_update_dialog(
                         let db_update = db_ref.clone();
                         let record_path = record_clone.path.clone();
                         let new_version = check_result.latest_version.clone();
-                        dialog_ref.connect_response(None, move |dlg, response| {
-                            if response == "update" {
-                                start_update(
-                                    dlg,
-                                    &record_path,
-                                    &download_url,
-                                    record_id,
-                                    new_version.as_deref(),
-                                    &db_update,
-                                );
-                            }
+                        dialog_ref.connect_response(Some("update"), move |dlg, _response| {
+                            start_update(
+                                dlg,
+                                &record_path,
+                                &download_url,
+                                record_id,
+                                new_version.as_deref(),
+                                &db_update,
+                            );
                         });
                     }
                 } else {
@@ -239,11 +237,9 @@ fn handle_old_version_cleanup(dialog: &adw::AlertDialog, old_path: PathBuf) {
             dialog.set_response_appearance("remove-old", adw::ResponseAppearance::Destructive);
 
             let path = old_path.clone();
-            dialog.connect_response(None, move |_dlg, response| {
-                if response == "remove-old" {
-                    if path.exists() {
-                        std::fs::remove_file(&path).ok();
-                    }
+            dialog.connect_response(Some("remove-old"), move |_dlg, _response| {
+                if path.exists() {
+                    std::fs::remove_file(&path).ok();
                 }
             });
         }

src/ui/widgets.rs

@@ -182,12 +182,10 @@ pub fn copy_button(text_to_copy: &str, toast_overlay: Option<&adw::ToastOverlay>
     let text = text_to_copy.to_string();
     let toast = toast_overlay.cloned();
     btn.connect_clicked(move |button| {
-        if let Some(display) = button.display().into() {
-            let clipboard = gtk::gdk::Display::clipboard(&display);
-            clipboard.set_text(&text);
-            if let Some(ref overlay) = toast {
-                overlay.add_toast(adw::Toast::new("Copied to clipboard"));
-            }
+        let clipboard = button.display().clipboard();
+        clipboard.set_text(&text);
+        if let Some(ref overlay) = toast {
+            overlay.add_toast(adw::Toast::new("Copied to clipboard"));
         }
     });
     btn