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/window.rs

@@ -614,8 +614,8 @@ impl DriftwoodWindow {
                         launcher::launch_appimage(&bg_db, record_id, appimage_path, "gui_context", &launch_args, &[])
                     }).await;
                     match result {
-                        Ok(launcher::LaunchResult::Started { child, method }) => {
-                            log::info!("Launched: {} (PID: {}, method: {})", path_str, child.id(), method.as_str());
+                        Ok(launcher::LaunchResult::Started { pid, method }) => {
+                            log::info!("Launched: {} (PID: {}, method: {})", path_str, pid, method.as_str());
                         }
                         Ok(launcher::LaunchResult::Crashed { exit_code, stderr, method }) => {
                             log::error!("App crashed (exit {}, method: {}): {}", exit_code.unwrap_or(-1), method.as_str(), stderr);