fix: 修复图片显示问题，添加whitenoise优化静态文件性能

backend/competition/serializers.py

@@ -1,8 +1,16 @@
 from rest_framework import serializers
+from django.conf import settings
 from .models import Competition, CompetitionEnrollment, ScoreDimension, Project, ProjectFile, Score, Comment, HomePageConfig, CarouselItem
 from shop.serializers import WeChatUserSerializer
 
 
+def _media_url(file_field):
+    """返回 media 文件的相对路径，避免 build_absolute_uri 生成容器内部地址"""
+    if file_field and file_field.name:
+        return settings.MEDIA_URL + file_field.name
+    return None
+
+
 class CarouselItemSerializer(serializers.ModelSerializer):
     display_image = serializers.SerializerMethodField()
     
@@ -13,9 +21,7 @@ class CarouselItemSerializer(serializers.ModelSerializer):
                   'order', 'is_active']
     
     def get_display_image(self, obj):
-        if obj.image:
-            return obj.image.url
-        return obj.image_url
+        return _media_url(obj.image) or obj.image_url
 
 
 class HomePageConfigSerializer(serializers.ModelSerializer):
@@ -30,9 +36,7 @@ class HomePageConfigSerializer(serializers.ModelSerializer):
                   'organizer', 'undertaker', 'carousel1_items', 'carousel2_items']
 
     def get_display_banner(self, obj):
-        if obj.banner_image:
-            return obj.banner_image.url
-        return obj.banner_image_url
+        return _media_url(obj.banner_image) or obj.banner_image_url
 
     def get_carousel1_items(self, obj):
         items = CarouselItem.objects.filter(carousel_type='carousel1', is_active=True)
@@ -62,9 +66,7 @@ class CompetitionSerializer(serializers.ModelSerializer):
                   'score_dimensions', 'created_at']
 
     def get_display_cover_image(self, obj):
-        if obj.cover_image:
-            return obj.cover_image.url
-        return obj.cover_image_url
+        return _media_url(obj.cover_image) or obj.cover_image_url
 
 
 class CompetitionEnrollmentSerializer(serializers.ModelSerializer):
@@ -109,9 +111,7 @@ class ProjectSerializer(serializers.ModelSerializer):
         }
 
     def get_display_cover_image(self, obj):
-        if obj.cover_image:
-            return obj.cover_image.url
-        return obj.cover_image_url
+        return _media_url(obj.cover_image) or obj.cover_image_url
 
 
 class ScoreSerializer(serializers.ModelSerializer):