Implement asset upload API and utility functions

- Add Asset and CardLayer model updates
- Create asset upload API endpoints
- Add AssetUploadDialog component
- Create card layout algorithms
- Implement symmetry generation utils
- Add template configurations

backend/apps/projects/serializers.py

@@ -1,4 +1,5 @@
 from rest_framework import serializers
+from django.conf import settings
 from .models import Project, Asset, CardLayer
 
 
@@ -9,10 +10,20 @@ class ProjectSerializer(serializers.ModelSerializer):
 
 
 class AssetSerializer(serializers.ModelSerializer):
+    file_url = serializers.SerializerMethodField()
+
     class Meta:
         model = Asset
         fields = '__all__'
 
+    def get_file_url(self, obj):
+        if obj.file_path:
+            request = self.context.get('request')
+            if request:
+                return request.build_absolute_uri(f'{settings.MEDIA_URL}{obj.file_path}')
+            return f'{settings.MEDIA_URL}{obj.file_path}'
+        return None
+
 
 class CardLayerSerializer(serializers.ModelSerializer):
     class Meta: