feat: 添加前后端多语言支持

前端：
- 在 API 请求中添加 Accept-Language 头，传递当前语言设置

后端：
- 创建 LanguageMiddleware 中间件，自动检测并设置语言
- 为所有 API 路由添加语言中间件

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

backend/config/route.php

@@ -2,11 +2,15 @@
 
 use Webman\Route;
 
+// 全局 API 中间件（语言设置）
+$apiMiddleware = [app\middleware\LanguageMiddleware::class];
+$authMiddleware = array_merge($apiMiddleware, [app\middleware\AuthMiddleware::class]);
+
 // 认证路由（不需要认证）
 Route::group('/api/v1', function () {
     Route::post('/auth/login', [app\controller\AuthController::class, 'login']);
     Route::post('/auth/feishu-login', [app\controller\AuthController::class, 'feishuLogin']);
-});
+})->middleware($apiMiddleware);
 
 // 用户路由（需要认证）
 Route::group('/api/v1/user', function () {
@@ -15,7 +19,7 @@ Route::group('/api/v1/user', function () {
     Route::get('/companies', [app\controller\UserController::class, 'companies']);
     Route::get('/list', [app\controller\UserController::class, 'list']);
     Route::post('/switch-company', [app\controller\UserController::class, 'switchCompany']);
-})->middleware([\app\middleware\AuthMiddleware::class]);
+})->middleware($authMiddleware);
 
 // 审批路由（需要认证）
 Route::group('/api/v1/approval', function () {
@@ -24,7 +28,7 @@ Route::group('/api/v1/approval', function () {
     Route::post('/approve/{id}', [app\controller\ApprovalController::class, 'approve']);
     Route::post('/reject/{id}', [app\controller\ApprovalController::class, 'reject']);
     Route::post('/cancel/{id}', [app\controller\ApprovalController::class, 'cancel']);
-})->middleware([\app\middleware\AuthMiddleware::class]);
+})->middleware($authMiddleware);
 
 // 出差审批路由（需要认证）
 Route::group('/api/v1/business-trip', function () {
@@ -36,7 +40,7 @@ Route::group('/api/v1/business-trip', function () {
     Route::post('/cancel/{id}', [app\controller\BusinessTripController::class, 'cancel']);
     Route::delete('/{id}', [app\controller\BusinessTripController::class, 'deleteDraft']);
     Route::post('/approve/{id}', [app\controller\BusinessTripController::class, 'approve']);
-})->middleware([\app\middleware\AuthMiddleware::class]);
+})->middleware($authMiddleware);
 
 // 默认路由
 Route::fallback(function () {