meta: integrate wallpaper, FileBrowser, StateLayer

- A lot of this is implements patterns implemented by soramannew's
  caelestia-shell

Modules/WallpaperBackground.qml

@@ -0,0 +1,63 @@
+import QtQuick
+import Quickshell
+import Quickshell.Wayland
+import Quickshell.Widgets
+import qs.Common
+import qs.Widgets
+
+Variants {
+    model: Quickshell.screens
+
+    PanelWindow {
+        id: wallpaperWindow
+
+        property var modelData
+
+        screen: modelData
+
+        WlrLayershell.layer: WlrLayer.Background
+        WlrLayershell.exclusionMode: ExclusionMode.Ignore
+        WlrLayershell.keyboardFocus: WlrKeyboardFocus.None
+
+        anchors.top: true
+        anchors.bottom: true  
+        anchors.left: true
+        anchors.right: true
+
+        visible: true
+        color: "transparent"
+
+        Image {
+            id: wallpaperImage
+
+            anchors.fill: parent
+            source: Prefs.wallpaperPath ? "file://" + Prefs.wallpaperPath : ""
+            fillMode: Image.PreserveAspectCrop
+            visible: Prefs.wallpaperPath !== ""
+            smooth: true
+            cache: true
+
+            // Smooth transition when wallpaper changes
+            Behavior on opacity {
+                NumberAnimation {
+                    duration: Appearance.anim.durations.normal
+                    easing.type: Easing.BezierSpline
+                    easing.bezierCurve: Appearance.anim.curves.standard
+                }
+            }
+
+            onStatusChanged: {
+                if (status === Image.Error) {
+                    console.warn("Failed to load wallpaper:", source);
+                }
+            }
+        }
+
+        // Fallback background color when no wallpaper is set
+        StyledRect {
+            anchors.fill: parent
+            color: Theme.surface
+            visible: !wallpaperImage.visible
+        }
+    }
+}