Feature: Add monitor-switch buttons to remote toolbars (#15342)

* Feature: add monitor-switch buttons to remote toolbars

Add buttons to cycle through the remote displays from the toolbars:

- A main-toolbar button and a minimized-handle button, both using a shared SVG icon with the current monitor number overlaid.
- Two opt-in settings under Settings/Other. The minimized-toolbar option is nested under the main-toolbar option.
- The minimized button only appears once the toolbar is collapsed.
- Cycling does not move the remote cursor, matching the existing in-toolbar monitor buttons.

Signed-off-by: StealUrKill <35749471+StealUrKill@users.noreply.github.com>

* fix: respect individual-window display mode when cycling

In "Show displays as individual windows" mode, route the cycle button through openMonitorInNewTabOrWindow like the monitor selector, so each display keeps its own window instead of repurposing the current one.

Signed-off-by: StealUrKill <35749471+StealUrKill@users.noreply.github.com>

---------

Signed-off-by: StealUrKill <35749471+StealUrKill@users.noreply.github.com>

flutter/lib/desktop/pages/desktop_setting_page.dart

@@ -407,6 +407,7 @@ class _GeneralState extends State<_General> {
   final RxBool serviceStop =
       isWeb ? RxBool(false) : Get.find<RxBool>(tag: 'stop-service');
   RxBool serviceBtnEnabled = true.obs;
+  final GlobalKey _minToolbarOptionKey = GlobalKey();
 
   @override
   Widget build(BuildContext context) {
@@ -605,6 +606,47 @@ class _GeneralState extends State<_General> {
         },
       ));
     }
+    children.add(_OptionCheckBox(
+      context,
+      'Show monitor switch button on the main toolbar',
+      kOptionAllowMonitorSwitchMainToolbar,
+      isServer: false,
+      update: (enabled) async {
+        if (!enabled) {
+          await mainSetLocalBoolOption(
+              kOptionAllowMonitorSwitchMinToolbar, false);
+        }
+        if (mounted) setState(() {});
+        reloadAllWindows();
+        if (enabled) {
+          WidgetsBinding.instance.addPostFrameCallback((_) {
+            final ctx = _minToolbarOptionKey.currentContext;
+            if (ctx != null) {
+              Scrollable.ensureVisible(
+                ctx,
+                alignment: 0.5,
+                duration: const Duration(milliseconds: 250),
+                curve: Curves.easeInOut,
+              );
+            }
+          });
+        }
+      },
+    ));
+    if (mainGetLocalBoolOptionSync(kOptionAllowMonitorSwitchMainToolbar)) {
+      children.add(KeyedSubtree(
+        key: _minToolbarOptionKey,
+        child: _OptionCheckBox(
+          context,
+          'Show on the minimized toolbar',
+          kOptionAllowMonitorSwitchMinToolbar,
+          isServer: false,
+          update: (_) {
+            reloadAllWindows();
+          },
+        ).marginOnly(left: _kCheckBoxLeftMargin * 3),
+      ));
+    }
     return _Card(title: 'Other', children: children);
   }