feat: 添加双屏控制功能，支持在第二块屏幕上全屏展示内容；更新相关 UI 和逻辑以适应新功能

src-tauri/capabilities/default.json

@@ -2,7 +2,7 @@
   "$schema": "../gen/schemas/desktop-schema.json",
   "identifier": "default",
   "description": "Capability for the main window",
-  "windows": ["main"],
+  "windows": ["main", "secondary"],
   "permissions": [
     "core:default",
     "core:window:default",