feat: 添加所有 Django apps 的 Serializers

- User Serializers（基础、详情、更新、统计）
- Region Serializers（基础、详情、树形结构）
- Moderation Serializers（版主申请、权限、支持、限制）
- Article Serializers（基础、创建、更新、审核、列表）
- FeaturedService Serializers（基础、创建、更新、审核、列表）
- Interaction Serializers（评论、评分、点赞、收藏）

backend/apps/interactions/serializers.py

@@ -0,0 +1,117 @@
+from rest_framework import serializers
+from .models import Comment, Rating, Like, Favorite
+
+
+class CommentSerializer(serializers.ModelSerializer):
+    """Serializer for Comment model."""
+
+    target_type_display = serializers.CharField(source='get_target_type_display', read_only=True)
+    ai_status_display = serializers.CharField(source='get_ai_status_display', read_only=True)
+    author_username = serializers.CharField(source='author.username', read_only=True)
+
+    class Meta:
+        model = Comment
+        fields = ('id', 'content', 'target_type', 'target_type_display', 'target_id',
+                  'author', 'author_username', 'ai_status', 'ai_status_display',
+                  'ai_rejection_reason', 'created_at')
+        read_only_fields = ('id', 'author', 'ai_status', 'ai_rejection_reason', 'created_at')
+
+    def create(self, validated_data):
+        validated_data['author'] = self.context['request'].user
+        return super().create(validated_data)
+
+
+class CommentCreateSerializer(serializers.ModelSerializer):
+    """Serializer for creating comments."""
+
+    class Meta:
+        model = Comment
+        fields = ('content', 'target_type', 'target_id')
+
+    def create(self, validated_data):
+        validated_data['author'] = self.context['request'].user
+        return super().create(validated_data)
+
+
+class RatingSerializer(serializers.ModelSerializer):
+    """Serializer for Rating model."""
+
+    target_type_display = serializers.CharField(source='get_target_type_display', read_only=True)
+    user_username = serializers.CharField(source='user.username', read_only=True)
+
+    class Meta:
+        model = Rating
+        fields = ('id', 'user', 'user_username', 'target_type', 'target_type_display',
+                  'target_id', 'score', 'created_at')
+        read_only_fields = ('id', 'user', 'created_at')
+
+    def create(self, validated_data):
+        validated_data['user'] = self.context['request'].user
+        return super().create(validated_data)
+
+
+class RatingCreateSerializer(serializers.ModelSerializer):
+    """Serializer for creating/updating ratings."""
+
+    class Meta:
+        model = Rating
+        fields = ('target_type', 'target_id', 'score')
+
+    def create(self, validated_data):
+        validated_data['user'] = self.context['request'].user
+        # Check if rating already exists
+        Rating.objects.filter(
+            user=validated_data['user'],
+            target_type=validated_data['target_type'],
+            target_id=validated_data['target_id']
+        ).delete()
+        return super().create(validated_data)
+
+
+class LikeSerializer(serializers.ModelSerializer):
+    """Serializer for Like model."""
+
+    target_type_display = serializers.CharField(source='get_target_type_display', read_only=True)
+    user_username = serializers.CharField(source='user.username', read_only=True)
+
+    class Meta:
+        model = Like
+        fields = ('id', 'user', 'user_username', 'target_type', 'target_type_display',
+                  'target_id', 'created_at')
+        read_only_fields = ('id', 'user', 'created_at')
+
+
+class FavoriteSerializer(serializers.ModelSerializer):
+    """Serializer for Favorite model."""
+
+    target_type_display = serializers.CharField(source='get_target_type_display', read_only=True)
+    user_username = serializers.CharField(source='user.username', read_only=True)
+
+    class Meta:
+        model = Favorite
+        fields = ('id', 'user', 'user_username', 'target_type', 'target_type_display',
+                  'target_id', 'created_at')
+        read_only_fields = ('id', 'user', 'created_at')
+
+
+class FavoriteCreateSerializer(serializers.ModelSerializer):
+    """Serializer for creating/removing favorites."""
+
+    class Meta:
+        model = Favorite
+        fields = ('target_type', 'target_id')
+
+    def create(self, validated_data):
+        validated_data['user'] = self.context['request'].user
+        # Check if favorite already exists
+        existing = Favorite.objects.filter(
+            user=validated_data['user'],
+            target_type=validated_data['target_type'],
+            target_id=validated_data['target_id']
+        ).first()
+
+        if existing:
+            existing.delete()
+            return None  # Return None to indicate removal
+
+        return super().create(validated_data)