Merge upstream/main: sync latest updates

- feat(gateway): aggregate all text chunks in non-streaming Gemini responses
- feat(gateway): add SUGGESTION MODE request interception
- feat(oauth): support Anthropic Team accounts with sk authorization
- fix(oauth): update Anthropic OAuth parameters to sync with latest client
- feat: add PromoCodeEnabled setting (default: true)
- resolved conflict: keep TianShuAPI site name while adding PromoCode feature

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

backend/internal/service/auth_service.go

@@ -153,8 +153,8 @@ func (s *AuthService) RegisterWithVerification(ctx context.Context, email, passw
 		return "", nil, ErrServiceUnavailable
 	}
 
-	// 应用优惠码（如果提供）
-	if promoCode != "" && s.promoService != nil {
+	// 应用优惠码（如果提供且功能已启用）
+	if promoCode != "" && s.promoService != nil && s.settingService != nil && s.settingService.IsPromoCodeEnabled(ctx) {
 		if err := s.promoService.ApplyPromoCode(ctx, user.ID, promoCode); err != nil {
 			// 优惠码应用失败不影响注册，只记录日志
 			log.Printf("[Auth] Failed to apply promo code for user %d: %v", user.ID, err)