plugins/desktop-widgets: create a new "desktop" widget plugin type

- Draggable per-monitor background layer widgets
- Add basic dms version checks on plugins
- Clock: built-in clock desktop plugin
- dgop: built-in system monitor desktop plugin

quickshell/Modules/Settings/Widgets/SettingsDisplayPicker.qml

@@ -0,0 +1,81 @@
+pragma ComponentBehavior: Bound
+
+import QtQuick
+import Quickshell
+import qs.Common
+import qs.Widgets
+
+Item {
+    id: root
+
+    property var displayPreferences: []
+
+    signal preferencesChanged(var preferences)
+
+    readonly property bool allDisplaysEnabled: {
+        if (!Array.isArray(displayPreferences))
+            return true;
+        return displayPreferences.includes("all") || displayPreferences.length === 0;
+    }
+
+    width: parent?.width ?? 0
+    height: displayColumn.height + Theme.spacingM * 2
+
+    Column {
+        id: displayColumn
+        width: parent.width - Theme.spacingM * 2
+        x: Theme.spacingM
+        anchors.verticalCenter: parent.verticalCenter
+        spacing: Theme.spacingM
+
+        StyledText {
+            text: I18n.tr("Displays")
+            font.pixelSize: Theme.fontSizeMedium
+            color: Theme.surfaceText
+        }
+
+        DankToggle {
+            width: parent.width
+            text: I18n.tr("All displays")
+            checked: root.allDisplaysEnabled
+            onToggled: isChecked => root.preferencesChanged(isChecked ? ["all"] : [])
+        }
+
+        Column {
+            width: parent.width
+            spacing: Theme.spacingXS
+            visible: !root.allDisplaysEnabled
+
+            Repeater {
+                model: Quickshell.screens
+
+                DankToggle {
+                    required property var modelData
+
+                    width: parent.width
+                    text: SettingsData.getScreenDisplayName(modelData)
+                    description: modelData.width + "×" + modelData.height
+                    checked: {
+                        const prefs = root.displayPreferences;
+                        if (!Array.isArray(prefs) || prefs.includes("all"))
+                            return false;
+                        return prefs.some(p => p.name === modelData.name);
+                    }
+                    onToggled: isChecked => {
+                        var prefs = root.displayPreferences;
+                        if (!Array.isArray(prefs) || prefs.includes("all"))
+                            prefs = [];
+                        prefs = prefs.filter(p => p.name !== modelData.name);
+                        if (isChecked) {
+                            prefs.push({
+                                name: modelData.name,
+                                model: modelData.model || ""
+                            });
+                        }
+                        root.preferencesChanged(prefs);
+                    }
+                }
+            }
+        }
+    }
+}