feat: add Kirigami app skeleton with libmpv playback

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

src/qml/Main.qml

@@ -0,0 +1,32 @@
+import QtQuick
+import org.kde.kirigami as Kirigami
+import org.kde.kirigamiaddons.formcard as FormCard
+
+Kirigami.ApplicationWindow {
+    id: root
+
+    // Set from C++ (main.cpp) when a file is passed on the command line.
+    required property url initialUrl
+
+    width: Kirigami.Units.gridUnit * 50
+    height: Kirigami.Units.gridUnit * 32
+    minimumWidth: Kirigami.Units.gridUnit * 20
+    minimumHeight: Kirigami.Units.gridUnit * 14
+
+    title: player.mediaTitle.length > 0 ? player.mediaTitle : "QtPotato"
+
+    pageStack.initialPage: PlayerPage {
+        id: player
+        initialUrl: root.initialUrl
+        onAboutRequested: root.pageStack.layers.push(aboutPage)
+        onFullScreenToggled: root.visibility = root.visibility === Window.FullScreen ? Window.Windowed : Window.FullScreen
+    }
+
+    pageStack.globalToolBar.style: Kirigami.ApplicationHeaderStyle.ToolBar
+    pageStack.columnView.columnResizeMode: Kirigami.ColumnView.SingleColumn
+
+    Component {
+        id: aboutPage
+        FormCard.AboutPage {}
+    }
+}