v0.0.36 | Upbit API 자격증명 관리 기능 추가

- CustomUser 모델에 Upbit access/secret key 암호화 필드 추가
- UpbitCredentialsView: 자격증명 저장/조회(마스킹)/삭제 API
- UpbitSecretKeyView: 복호화된 키 조회 API (내부 서비스 호출용)
- 마이그레이션 파일 추가

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

users/views.py

@@ -2075,3 +2075,109 @@ class SiteSettingsView(APIView):
             # 메타 정보
             "updated_at": settings_obj.updated_at.isoformat() if settings_obj.updated_at else None,
         })
+
+
+# ============================================
+# 📈 Upbit API 자격증명 관리
+# ============================================
+
+class UpbitCredentialsView(APIView):
+    """Upbit API 자격증명 저장/조회/삭제"""
+    permission_classes = [IsAuthenticated]
+
+    def get(self, request):
+        """자격증명 조회 (키 마스킹)"""
+        enrich_span(request, request.user, operation="upbit.credentials.get")
+        email, ip, ua = get_request_info(request)
+        user = request.user
+
+        with child_span("get_credentials", user_id=user.id):
+            has_credentials = bool(user.encrypted_upbit_access_key and user.encrypted_upbit_secret_key)
+            access_key_masked = ""
+            if has_credentials:
+                try:
+                    ak = user.decrypt_upbit_access_key()
+                    access_key_masked = ak[:4] + "****" + ak[-4:] if len(ak) > 8 else "****"
+                except Exception:
+                    access_key_masked = "****"
+
+        span_success(200)
+        return Response({
+            "has_credentials": has_credentials,
+            "access_key": access_key_masked,
+        })
+
+    def post(self, request):
+        """자격증명 저장"""
+        enrich_span(request, request.user, operation="upbit.credentials.save")
+        email, ip, ua = get_request_info(request)
+        user = request.user
+
+        access_key = request.data.get("access_key")
+        secret_key = request.data.get("secret_key")
+
+        if not access_key or not secret_key:
+            span_error("missing_fields", 400)
+            return Response(
+                {"error": "access_key, secret_key는 필수입니다."},
+                status=status.HTTP_400_BAD_REQUEST,
+            )
+
+        try:
+            with child_span("encrypt_and_save"):
+                user.save_upbit_credentials(access_key, secret_key)
+
+            logger.info(f"[UPBIT CREDENTIALS SAVE] user={email} | status=success | IP={ip}")
+            span_success(201)
+            return Response({"message": "Upbit API 키가 저장되었습니다."}, status=201)
+        except Exception as e:
+            logger.exception(f"[UPBIT CREDENTIALS SAVE] user={email} | status=fail | IP={ip}")
+            span_error(str(e), 500)
+            return Response({"error": f"저장 실패: {str(e)}"}, status=500)
+
+    def delete(self, request):
+        """자격증명 삭제"""
+        enrich_span(request, request.user, operation="upbit.credentials.delete")
+        email, ip, ua = get_request_info(request)
+        user = request.user
+
+        with child_span("delete_credentials", user_id=user.id):
+            user.clear_upbit_credentials()
+
+        logger.info(f"[UPBIT CREDENTIALS DELETE] user={email} | status=success | IP={ip}")
+        span_success(200)
+        return Response({"message": "Upbit API 키가 삭제되었습니다."})
+
+
+class UpbitSecretKeyView(APIView):
+    """Upbit API 키 조회 (복호화) - msa-django-upbit에서 호출용"""
+    permission_classes = [IsAuthenticated]
+
+    def get(self, request):
+        """복호화된 API 키 조회"""
+        enrich_span(request, request.user, operation="upbit.keys.get")
+        email, ip, ua = get_request_info(request)
+        user = request.user
+
+        if not user.encrypted_upbit_access_key or not user.encrypted_upbit_secret_key:
+            span_error("not_found", 404)
+            return Response(
+                {"error": "Upbit API 키가 등록되어 있지 않습니다."},
+                status=404
+            )
+
+        try:
+            with child_span("decrypt_keys"):
+                access_key = user.decrypt_upbit_access_key()
+                secret_key = user.decrypt_upbit_secret_key()
+
+            logger.info(f"[UPBIT KEYS GET] user={email} | status=success | IP={ip}")
+            span_success(200)
+            return Response({
+                "access_key": access_key,
+                "secret_key": secret_key,
+            })
+        except Exception as e:
+            logger.exception(f"[UPBIT KEYS GET] user={email} | status=fail | IP={ip}")
+            span_error(str(e), 500)
+            return Response({"error": f"키 복호화 실패: {str(e)}"}, status=500)