refactor: align project directory architecture

apps/desktop/src/shell/AppFrame.tsx

@@ -0,0 +1,20 @@
+import { Outlet } from "react-router-dom";
+import { desktopPlatform } from "../shared/native/platform";
+import styles from "./AppFrame.module.scss";
+import { AppHeader } from "./AppHeader";
+
+const currentPlatform = desktopPlatform();
+document.documentElement.dataset.platform = currentPlatform;
+
+export function AppFrame() {
+  const platform = currentPlatform;
+  const platformClasses = platform === "windows" ? [styles.windows] : [];
+  const nativeDesktop = "__TAURI_INTERNALS__" in window;
+
+  return (
+    <div className={[styles.shell, ...platformClasses].filter(Boolean).join(" ")}>
+      <AppHeader platform={platform} nativeDesktop={nativeDesktop} />
+      <Outlet />
+    </div>
+  );
+}