feat(notifications): implement notification service

windows/Notification.qml

@@ -0,0 +1,55 @@
+pragma ComponentBehavior: Bound
+
+import QtQuick
+import QtQuick.Layouts
+import Quickshell
+import qs.config
+import qs.services
+import "../modules/osd"
+
+PanelWindow {
+  id: root
+
+  readonly property int cardWidth: 420
+
+  color: "transparent"
+  exclusionMode: ExclusionMode.Ignore
+  visible: Notifications.popupCount > 0
+  implicitWidth: root.cardWidth
+  implicitHeight: stack.implicitHeight
+
+  anchors {
+    top: true
+    right: true
+  }
+  margins {
+    top: 50 + Appearance.margin
+    right: 10 + Appearance.margin
+  }
+
+  mask: Region {
+    item: stack
+  }
+
+  ColumnLayout {
+    id: stack
+
+    anchors.top: parent.top
+    anchors.right: parent.right
+    anchors.left: parent.left
+    spacing: Appearance.spacing
+
+    Repeater {
+      model: [...Notifications.popups.values].reverse()
+
+      NotificationCard {
+        id: card
+
+        required property var modelData
+
+        notif: modelData
+        Layout.fillWidth: true
+      }
+    }
+  }
+}