Add Ctrl+A and Ctrl+Shift+A keyboard shortcuts for select/deselect all

- Register select-all-images and deselect-all-images actions
- Wire Ctrl+A to clear exclusion set, Ctrl+Shift+A to exclude all
- Both shortcuts update checkbox state and count label in images step
- Make set_all_checkboxes_in public for cross-module access

pixstrip-gtk/src/app.rs

@@ -128,6 +128,8 @@ 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("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"]);
@@ -441,6 +443,54 @@ fn setup_window_actions(window: &adw::ApplicationWindow, ui: &WizardUi) {
         action_group.add_action(&action);
     }
 
+    // Select all images action
+    {
+        let ui = ui.clone();
+        let action = gtk::gio::SimpleAction::new("select-all-images", None);
+        action.connect_activate(move |_, _| {
+            ui.state.excluded_files.borrow_mut().clear();
+            // Update the images step UI
+            if let Some(page) = ui.pages.get(1)
+                && let Some(stack) = page.child().and_downcast::<gtk::Stack>()
+                && let Some(loaded) = stack.child_by_name("loaded")
+            {
+                crate::steps::step_images::set_all_checkboxes_in(&loaded, true);
+                let files = ui.state.loaded_files.borrow();
+                let count = files.len();
+                drop(files);
+                update_images_count_label(&ui, count);
+            }
+        });
+        action_group.add_action(&action);
+    }
+
+    // Deselect all images action
+    {
+        let ui = ui.clone();
+        let action = gtk::gio::SimpleAction::new("deselect-all-images", None);
+        action.connect_activate(move |_, _| {
+            {
+                let files = ui.state.loaded_files.borrow();
+                let mut excl = ui.state.excluded_files.borrow_mut();
+                for f in files.iter() {
+                    excl.insert(f.clone());
+                }
+            }
+            // Update the images step UI
+            if let Some(page) = ui.pages.get(1)
+                && let Some(stack) = page.child().and_downcast::<gtk::Stack>()
+                && let Some(loaded) = stack.child_by_name("loaded")
+            {
+                crate::steps::step_images::set_all_checkboxes_in(&loaded, false);
+                let files = ui.state.loaded_files.borrow();
+                let count = files.len();
+                drop(files);
+                update_images_count_label(&ui, count);
+            }
+        });
+        action_group.add_action(&action);
+    }
+
     // Settings action - opens settings dialog
     {
         let window = window.clone();

pixstrip-gtk/src/steps/step_images.rs

@@ -437,7 +437,7 @@ fn build_loaded_state(state: &AppState) -> gtk::Box {
                 && let Some(stack) = parent.downcast_ref::<gtk::Stack>()
                 && let Some(loaded_widget) = stack.child_by_name("loaded")
             {
-                set_all_checkboxes(&loaded_widget, true);
+                set_all_checkboxes_in(&loaded_widget, true);
                 update_count_label(&loaded_widget, &loaded, &excl);
             }
         });
@@ -459,7 +459,7 @@ fn build_loaded_state(state: &AppState) -> gtk::Box {
                 && let Some(stack) = parent.downcast_ref::<gtk::Stack>()
                 && let Some(loaded_widget) = stack.child_by_name("loaded")
             {
-                set_all_checkboxes(&loaded_widget, false);
+                set_all_checkboxes_in(&loaded_widget, false);
                 update_count_label(&loaded_widget, &loaded, &excl);
             }
         });
@@ -498,14 +498,14 @@ fn build_loaded_state(state: &AppState) -> gtk::Box {
 }
 
 /// Set all CheckButton widgets within a container to a given state
-fn set_all_checkboxes(widget: &gtk::Widget, active: bool) {
+pub fn set_all_checkboxes_in(widget: &gtk::Widget, active: bool) {
     if let Some(check) = widget.downcast_ref::<gtk::CheckButton>() {
         check.set_active(active);
         return; // Don't recurse into CheckButton children
     }
     let mut child = widget.first_child();
     while let Some(c) = child {
-        set_all_checkboxes(&c, active);
+        set_all_checkboxes_in(&c, active);
         child = c.next_sibling();
     }
 }