refactor: 迁移 i18n 系统从 react-i18next 到 chrome.i18n

- 移除 react-i18next、i18next 及相关依赖
- 删除旧的 i18n/ 目录和 useLazyTranslation 工具
- 新增 utils/chromeI18n.ts 类型安全 wrapper（useI18n Hook + getMessage）
- 生成 public/_locales/{zh,en}/messages.json（298 个翻译 key）
- 批量更新 39+ 组件文件的导入和翻译调用
- 转换翻译键格式：namespace:key → namespace_key
- 修复 ErrorBoundary/PageErrorBoundary 从 withTranslation HOC 改为直接调用 getMessage
- 更新 vitest.setup.ts mock 加载实际翻译文本
- 修复 11 个测试文件的断言以匹配中文翻译
- TypeScript、ESLint、547 项测试全部通过

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

pages/Base64Converter/__tests__/index.test.tsx

@@ -2,15 +2,6 @@ import { describe, expect, it, vi } from 'vitest';
 import { act, fireEvent, render, screen, waitFor } from '@testing-library/react';
 import Base64ConverterPage from '../index';
 
-// Mock useLazyTranslation
-vi.mock('@/utils/useLazyTranslation', () => ({
-  useLazyTranslation: () => ({
-    t: (key: string) => key,
-    i18n: { changeLanguage: vi.fn(), language: 'zh-CN' },
-    isLoaded: true,
-  }),
-}));
-
 // Mock getEntryPointType
 vi.mock('@/config/features', async (importOriginal) => {
   const actual = await importOriginal<typeof import('@/config/features')>();
@@ -49,15 +40,15 @@ describe('Base64ConverterPage', () => {
   it('应该渲染模式切换按钮', async () => {
     render(<Base64ConverterPage />);
     await waitForStorageInit();
-    expect(screen.getByText('base64Converter:textMode')).toBeInTheDocument();
-    expect(screen.getByText('base64Converter:fileMode')).toBeInTheDocument();
-    expect(screen.getByText('base64Converter:imageMode')).toBeInTheDocument();
+    expect(screen.getByText('文本')).toBeInTheDocument();
+    expect(screen.getByText('文件')).toBeInTheDocument();
+    expect(screen.getByText('图像')).toBeInTheDocument();
   });
 
   it('切换到文件模式应该渲染 FileMode', async () => {
     render(<Base64ConverterPage />);
     await waitForStorageInit();
-    fireEvent.click(screen.getByText('base64Converter:fileMode'));
+    fireEvent.click(screen.getByText('文件'));
     await waitFor(() => {
       expect(screen.getByTestId('file-mode')).toBeInTheDocument();
     });
@@ -67,7 +58,7 @@ describe('Base64ConverterPage', () => {
   it('切换到图像模式应该渲染 ImageMode', async () => {
     render(<Base64ConverterPage />);
     await waitForStorageInit();
-    fireEvent.click(screen.getByText('base64Converter:imageMode'));
+    fireEvent.click(screen.getByText('图像'));
     await waitFor(() => {
       expect(screen.getByTestId('image-mode')).toBeInTheDocument();
     });