Move remaining code to app module

There's still some stuff that could potentially go elsewhere but I think it's enough for now.

src/app/qml/ConfirmLeaveDialog.qml

@@ -0,0 +1,34 @@
+// SPDX-FileCopyrightText: 2024 Tobias Fella <tobias.fella@kde.org>
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+import QtQuick
+import QtQuick.Controls as QQC2
+
+import org.kde.kirigami as Kirigami
+
+import org.kde.neochat
+
+Kirigami.PromptDialog {
+    id: root
+
+    required property NeoChatRoom room
+
+    title: i18nc("@title:dialog", "Confirm Leaving Room")
+    subtitle: root.room ? i18nc("Do you really want to leave <room name>?", "Do you really want to leave %1?", root.room.displayNameForHtml) : ""
+    dialogType: Kirigami.PromptDialog.Warning
+
+    onRejected: {
+        root.close();
+    }
+
+    footer: QQC2.DialogButtonBox {
+        standardButtons: QQC2.Dialog.Cancel
+
+        QQC2.Button {
+            text: i18nc("@action:button", "Leave Room")
+            QQC2.DialogButtonBox.buttonRole: QQC2.DialogButtonBox.AcceptRole
+            icon.name: "arrow-left-symbolic"
+            onClicked: RoomManager.leaveRoom(root.room)
+        }
+    }
+}