feat: Wallpapers built into the Media Hub

- Thanks @TaylanTatli for the inspiration

DMSGreeter.qml

@@ -1,11 +1,29 @@
 import QtQuick
 import Quickshell
+import Quickshell.Wayland
 import Quickshell.Services.Greetd
 import qs.Common
 import qs.Modules.Greetd
 
-Scope {
+Item {
     id: root
 
-    GreeterSurface {}
+    WlSessionLock {
+        id: sessionLock
+        locked: false
+
+        Component.onCompleted: {
+            Qt.callLater(() => { locked = true })
+        }
+
+        onLockedChanged: {
+            if (!locked) {
+                console.log("Greetd session unlocked, exiting")
+            }
+        }
+
+        GreeterSurface {
+            lock: sessionLock
+        }
+    }
 }