fix: add dispose() methods to prevent VRAM/GTT memory leaks

Add proper resource cleanup in dispose() methods for several widget classes
to prevent GPU memory (VRAM/GTT) leaks when notifications and media players
are created and destroyed.

Changes:
- Notification: Add dispose() to clear img, img_app_icon, body_image and
  remove pending timeouts. Also clear body_image before setting new paintable.
- MprisPlayer: Add dispose() and enhance before_destroy() to cancel downloads
  and clear album_art/background_picture textures. Clear textures before
  loading new album art.
- Underlay: Add dispose() to properly unparent children.
- NotificationGroup: Add dispose() to skip/null animations and clear collections.

These fixes address GPU memory accumulation observed when:
- Notifications with images are repeatedly shown and dismissed
- MPRIS players update album art frequently
- Notification groups are expanded/collapsed

Fixes potential VRAM/GTT memory leaks in GTK4/Wayland environments.

Author: Jeronimo Garcia

src/controlCenter/widgets/mpris/mpris_player.vala

@@ -98,8 +98,20 @@ namespace SwayNotificationCenter.Widgets.Mpris {
             album_art.set_visible (mpris_config.show_album_art == AlbumArtState.ALWAYS);
         }
 
+        public override void dispose () {
+            before_destroy ();
+            base.dispose ();
+        }
+
         public void before_destroy () {
             source.properties_changed.disconnect (properties_changed);
+
+            // Cancel any ongoing album art download
+            album_art_cancellable.cancel ();
+
+            // Clear album art textures to release VRAM/GPU memory
+            album_art.clear ();
+            background_picture.set_paintable (null);
         }
 
         private void properties_changed (string iface,
@@ -263,6 +275,10 @@ namespace SwayNotificationCenter.Widgets.Mpris {
                 // Cancel previous download, reset the state and download again
                 album_art_cancellable.cancel ();
                 album_art_cancellable.reset ();
+                
+                // Clear previous textures before loading new ones to release GPU memory
+                album_art.clear ();
+                background_picture.set_paintable (null);
 
                 Gdk.Texture ?album_art_texture = null;
                 try {

src/notification/notification.vala

@@ -105,6 +105,22 @@ namespace SwayNotificationCenter {
 
         private Notification () {}
 
+        public override void dispose () {
+            // Clear all image resources to release VRAM/GPU memory
+            img.clear ();
+            img_app_icon.clear ();
+            body_image.set_paintable (null);
+
+            // Remove any pending timeout
+            remove_noti_timeout ();
+
+            // Clear gesture/controller references
+            gesture = null;
+            motion_controller = null;
+
+            base.dispose ();
+        }
+
         /** Show a non-timed notification */
         public Notification.regular (NotifyParams param,
                                      NotificationType notification_type) {
@@ -344,6 +360,8 @@ namespace SwayNotificationCenter {
                         string img = Functions.uri_to_path (img_paths[0]);
                         File file = File.new_for_path (img);
                         if (img.length > 0 && file.query_exists ()) {
+                            // Clear previous body image to release GPU memory
+                            body_image.set_paintable (null);
                             Gdk.Texture texture = Gdk.Texture.from_file (file);
                             body_image.set_paintable (texture);
                             body_image.set_can_shrink (true);