feat: Attachment 모델 추가 및 관련 기능 구현

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

requirements.txt

@@ -1,4 +1,6 @@
 asgiref==3.8.1
+boto3==1.42.30
+botocore==1.42.30
 certifi==2025.1.31
 cffi==2.0.0
 charset-normalizer==3.4.1
@@ -7,6 +9,7 @@ coreschema==0.0.4
 cryptography==46.0.1
 Django==4.2.14
 django-cors-headers==4.7.0
+django-storages==1.14.6
 djangorestframework==3.16.0
 djangorestframework_simplejwt==5.5.0
 drf-yasg==1.21.10
@@ -15,15 +18,19 @@ idna==3.10
 inflection==0.5.1
 itypes==1.2.0
 Jinja2==3.1.6
+jmespath==1.0.1
 MarkupSafe==3.0.2
 mysqlclient==2.2.7
 packaging==25.0
 pycparser==2.23
 PyJWT==2.9.0
+python-dateutil==2.9.0.post0
 python-dotenv==1.0.1
 pytz==2025.2
 PyYAML==6.0.2
 requests==2.32.3
+s3transfer==0.16.0
+six==1.17.0
 sqlparse==0.5.3
 typing_extensions==4.13.2
 uritemplate==4.1.1