refactor: reorganize directory structure into src/

Move all source code directories into src/ for cleaner project structure:
- pages/, components/, utils/, config/, providers/, types/, lib/, assets/, entrypoints/ → src/
- Use WXT srcDir config to resolve @/ alias to src/
- Update tsconfig, vitest, eslint, tailwind configs
- Remove scattered README.md files from subdirectories
- Update documentation (AGENTS.md, CODING_STANDARDS.md, README.md)
- Fix pre-existing lint error in RouterProvider.tsx

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

src/pages/QrCode/__tests__/index.test.tsx

@@ -0,0 +1,89 @@
+import { beforeEach, describe, expect, it, vi } from 'vitest';
+import { fireEvent, render, screen } from '@testing-library/react';
+import QrCodePage from '../index';
+
+vi.mock('lucide-react', async (importOriginal) => {
+  const actual = await importOriginal<typeof import('lucide-react')>();
+  return {
+    ...actual,
+    // 增量伪造需要高精嗅探的 QrCode 核心定位图标
+    QrCode: () => <div data-testid="mock-lucide-qrcode">Icon</div>,
+  };
+});
+
+// Mock useSnackbar
+vi.mock('@/components/GlobalSnackbar', () => ({
+  useSnackbar: () => ({
+    showMessage: vi.fn(),
+  }),
+}));
+
+// Mock getEntryPointType（保留原厂其他特征配置，仅模拟入口路由环境）
+vi.mock('@/config/features', async (importOriginal) => {
+  const actual = await importOriginal<typeof import('@/config/features')>();
+  return {
+    ...actual,
+    getEntryPointType: () => 'sidepanel',
+  };
+});
+
+// Mock 高频变化的子组件，收拢断言边界
+vi.mock('@/components/QrCodePreview', () => ({
+  default: () => <div data-testid="qr-code-preview">QrCodePreview</div>,
+}));
+
+vi.mock('@/components/ImageUploader', () => ({
+  default: () => <div data-testid="image-uploader">ImageUploader</div>,
+}));
+
+// Mock QRious 动态图像离屏生成引擎
+vi.mock('qrious', () => ({
+  default: vi.fn().mockImplementation(() => ({
+    toDataURL: () => 'data:image/png;base64,mock',
+  })),
+}));
+
+describe('QrCodePage', () => {
+  beforeEach(() => {
+    vi.clearAllMocks();
+  });
+
+  it('应该默认渲染生成模式', () => {
+    render(<QrCodePage />);
+    expect(screen.getByTestId('qr-code-preview')).toBeInTheDocument();
+  });
+
+  it('应该渲染模式切换按钮', () => {
+    render(<QrCodePage />);
+    expect(screen.getByText('文本转二维码')).toBeInTheDocument();
+    expect(screen.getByText('二维码转文本')).toBeInTheDocument();
+  });
+
+  it('切换到解析模式应该渲染 ImageUploader', () => {
+    render(<QrCodePage />);
+    fireEvent.click(screen.getByText('二维码转文本'));
+    expect(screen.getByTestId('image-uploader')).toBeInTheDocument();
+    expect(screen.queryByTestId('qr-code-preview')).not.toBeInTheDocument();
+  });
+
+  it('切换回生成模式应该渲染 QrCodePreview', () => {
+    render(<QrCodePage />);
+    // 先切换到解析模式
+    fireEvent.click(screen.getByText('二维码转文本'));
+    expect(screen.getByTestId('image-uploader')).toBeInTheDocument();
+    // 再切换回生成模式
+    fireEvent.click(screen.getByText('文本转二维码'));
+    expect(screen.getByTestId('qr-code-preview')).toBeInTheDocument();
+  });
+
+  it('应该渲染输入区域的系统标签（对齐新版 Label 机制）', () => {
+    render(<QrCodePage />);
+    expect(screen.getByText('输入 URL 或文本')).toBeInTheDocument();
+  });
+
+  it('应该渲染双翼响应式卡片网格布局', () => {
+    const { container } = render(<QrCodePage />);
+    const gridContainer = container.querySelector('.grid');
+    expect(gridContainer).toBeInTheDocument();
+  });
+});