Add Ctrl+Z undo last batch and register select/deselect shortcuts

- Ctrl+Z moves output files from last batch to system trash via GIO
- Select all / deselect all actions now registered as window actions
- Shortcuts registered: Ctrl+A, Ctrl+Shift+A, Ctrl+Z

pixstrip-gtk/src/app.rs

@@ -130,6 +130,7 @@ fn setup_shortcuts(app: &adw::Application) {
     app.set_accels_for_action("win.add-files", &["<Control>o"]);
     app.set_accels_for_action("win.select-all-images", &["<Control>a"]);
     app.set_accels_for_action("win.deselect-all-images", &["<Control><Shift>a"]);
+    app.set_accels_for_action("win.undo-last-batch", &["<Control>z"]);
     app.set_accels_for_action("app.quit", &["<Control>q"]);
     app.set_accels_for_action("win.show-settings", &["<Control>comma"]);
     app.set_accels_for_action("win.show-shortcuts", &["<Control>question", "F1"]);
@@ -545,6 +546,16 @@ fn setup_window_actions(window: &adw::ApplicationWindow, ui: &WizardUi) {
         action_group.add_action(&action);
     }
 
+    // Undo last batch action
+    {
+        let ui = ui.clone();
+        let action = gtk::gio::SimpleAction::new("undo-last-batch", None);
+        action.connect_activate(move |_, _| {
+            undo_last_batch(&ui);
+        });
+        action_group.add_action(&action);
+    }
+
     // Keyboard shortcuts window
     {
         let window = window.clone();
@@ -1459,6 +1470,43 @@ fn wire_results_actions(
     });
 }
 
+fn undo_last_batch(ui: &WizardUi) {
+    let history = pixstrip_core::storage::HistoryStore::new();
+    let entries = match history.list() {
+        Ok(e) => e,
+        Err(_) => {
+            ui.toast_overlay.add_toast(adw::Toast::new("No processing history available"));
+            return;
+        }
+    };
+
+    let Some(last) = entries.last() else {
+        ui.toast_overlay.add_toast(adw::Toast::new("No batches to undo"));
+        return;
+    };
+
+    if last.output_files.is_empty() {
+        ui.toast_overlay.add_toast(adw::Toast::new("No output files recorded for last batch"));
+        return;
+    }
+
+    // Move output files to trash using GIO
+    let mut trashed = 0usize;
+    for path_str in &last.output_files {
+        let file = gtk::gio::File::for_path(path_str);
+        if file.trash(gtk::gio::Cancellable::NONE).is_ok() {
+            trashed += 1;
+        }
+    }
+
+    let toast = adw::Toast::new(&format!(
+        "Undo: moved {} files to trash",
+        trashed
+    ));
+    toast.set_timeout(5);
+    ui.toast_overlay.add_toast(toast);
+}
+
 fn reset_wizard(ui: &WizardUi) {
     // Reset state
     {