refactor: use shadcn sidebar

frontend/app/routes/system-projects.tsx

@@ -0,0 +1,23 @@
+import { useAuth } from "~/context/AuthContext";
+import { useScriptWorkspaceStore } from "~/features/platform/state/scriptWorkspaceStore";
+import { useUiStore } from "~/features/platform/state/uiStore";
+import { ProjectManagementPage } from "~/features/admin/ProjectManagementPage";
+
+/**
+ * /system/projects 路由页。ProjectManagementPage 内部有 useState，
+ * 在 user / workspace 切换时必须重挂载以重置本地状态
+ * （见 CLAUDE.md「Route components with their own internal state」）。
+ */
+export default function ProjectManagementRoute() {
+  const { user, currentWorkspace } = useAuth();
+  const setApiOnline = useScriptWorkspaceStore((s) => s.setApiOnline);
+  const pushToast = useUiStore((s) => s.pushToast);
+
+  return (
+    <ProjectManagementPage
+      key={`${user?.user_id ?? "anon"}-${currentWorkspace?.workspace_id ?? "none"}`}
+      onNotify={pushToast}
+      onConnectionChange={setApiOnline}
+    />
+  );
+}