fix: 提升管理端启动与导航稳定性

- 等待初始路由就绪并提供可恢复的启动失败页面

- 收敛失效登录导航并按需加载 SVG 图标资源

easyflow-ui-admin/app/src/startup-error.test.ts

@@ -0,0 +1,27 @@
+import { afterEach, describe, expect, it, vi } from 'vitest';
+
+import { renderStartupError } from './startup-error';
+
+describe('startup error fallback', () => {
+  afterEach(() => {
+    document.body.replaceChildren();
+  });
+
+  it('renders a recoverable error state and reloads on demand', () => {
+    const root = document.createElement('div');
+    const reload = vi.fn();
+    document.body.append(root);
+
+    expect(renderStartupError({ reload, root })).toBe(true);
+    expect(root.querySelector('[role="alert"]')).not.toBeNull();
+    expect(root.textContent).toContain('页面加载失败');
+
+    const retryButton = root.querySelector<HTMLButtonElement>('button');
+    retryButton?.click();
+    expect(reload).toHaveBeenCalledOnce();
+  });
+
+  it('returns false when the application root is missing', () => {
+    expect(renderStartupError({ root: null })).toBe(false);
+  });
+});