添加应用级别窗口按钮，以改善linux wayland下系统窗口按钮失效的问题 (#1119)

* feat(window): add app-level window controls with settings toggle

Add a persistent settings toggle to enable app-level minimize/maximize/close controls and hide system decorations when enabled, providing a Wayland-friendly fallback for broken native titlebar interactions.

Co-authored-by: Cursor <cursoragent@cursor.com>

* fix(window): restrict app-level window controls to Linux only and fix startup flicker

- Guard useAppWindowControls with isLinux() in App.tsx so it's always
  false on macOS/Windows even if persisted as true
- Wrap set_decorations call in lib.rs with #[cfg(target_os = "linux")]
- Only show the toggle in WindowSettings on Linux
- Skip setDecorations effect while settingsData is still loading to
  prevent the Rust-side decoration state from being overridden by the
  undefined->false fallback, which caused a brief title bar flicker

---------

Co-authored-by: wzk <wx13571681304@outlook.com>
Co-authored-by: Cursor <cursoragent@cursor.com>
Co-authored-by: Jason <farion1231@gmail.com>

src-tauri/capabilities/default.json

@@ -11,6 +11,11 @@
     "updater:default",
     "core:window:allow-set-skip-taskbar",
     "core:window:allow-start-dragging",
+    "core:window:allow-minimize",
+    "core:window:allow-toggle-maximize",
+    "core:window:allow-is-maximized",
+    "core:window:allow-close",
+    "core:window:allow-set-decorations",
     "process:allow-restart",
     "dialog:default"
   ]