QML: show daemon availability banner

Expose the Game Center daemon availability to the UI and show\nan inline error banner when it is not reachable, with a retry action.

src/qml/Main.qml

@@ -893,9 +893,30 @@ Kirigami.ApplicationWindow {
             }
         ]
 
+        ColumnLayout {
+            anchors.fill: parent
+            spacing: 0
+
+            Kirigami.InlineMessage {
+                id: daemonBanner
+                Layout.fillWidth: true
+                Layout.bottomMargin: Kirigami.Units.smallSpacing
+                type: Kirigami.MessageType.Error
+                visible: !App.launcher.daemonAvailable
+                text: i18n("Game Center daemon is not running. Game launching is unavailable.")
+                actions: [
+                    Kirigami.Action {
+                        text: i18n("Retry")
+                        icon.name: "view-refresh"
+                        onTriggered: App.launcher.retryDaemonConnection()
+                    }
+                ]
+            }
+
             LibraryView {
                 id: libraryView
-            anchors.fill: parent
+                Layout.fillWidth: true
+                Layout.fillHeight: true
 
                 filterSource: root.currentSource
                 searchActive: root.searchActive
@@ -913,6 +934,7 @@ Kirigami.ApplicationWindow {
                 }
             }
         }
+    }
 
     GameDetailsSheet {
         id: detailsSheet