feat: Add desktop scaling and fix linux postinst (#1800)

* fix: resolve Linux window close handler to prevent app hang

- Add delete-event callback that properly quits the application when window is closed

* feat: Add desktop scaling and fix linux postinst

- Implement desktop interface scaling in main.dart using FittedBox.
- Add desktop scaling setting UI.
- Add desktopScale to storage preference.
- Fix typos and logic in Linux postinst script.
- Update piliplus.desktop with StartupWMClass.

* update

Signed-off-by: dom <githubaccount56556@proton.me>

---------

Signed-off-by: Shao Guohao <shao.gh.98@gmail.com>
Co-authored-by: dom <githubaccount56556@proton.me>

lib/common/widgets/stateful_builder.dart

@@ -0,0 +1,36 @@
+import 'package:flutter/material.dart';
+
+class StatefulBuilder extends StatefulWidget {
+  const StatefulBuilder({
+    super.key,
+    this.onInit,
+    this.onDispose,
+    required this.builder,
+  });
+
+  final VoidCallback? onInit;
+
+  final VoidCallback? onDispose;
+
+  final StatefulWidgetBuilder builder;
+
+  @override
+  State<StatefulBuilder> createState() => _StatefulBuilderState();
+}
+
+class _StatefulBuilderState extends State<StatefulBuilder> {
+  @override
+  void initState() {
+    super.initState();
+    widget.onInit?.call();
+  }
+
+  @override
+  void dispose() {
+    widget.onDispose?.call();
+    super.dispose();
+  }
+
+  @override
+  Widget build(BuildContext context) => widget.builder(context, setState);
+}