Add NHN Cloud credentials management and bump version to v0.0.19

- Add NHN Cloud credential fields to User model (tenant_id, username, encrypted password, storage_account)
- Add API endpoints for credentials CRUD operations
- Implement Fernet encryption for password storage

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

users/models.py

@@ -71,6 +71,12 @@ class CustomUser(AbstractBaseUser, PermissionsMixin):
     encrypted_private_key = models.BinaryField(blank=True, null=True)
     last_used_at = models.DateTimeField(blank=True, null=True, verbose_name="SSH 키 마지막 사용 시각")
 
+    # ☁️ NHN Cloud 자격증명 필드
+    nhn_tenant_id = models.CharField(max_length=64, blank=True, null=True, verbose_name="NHN Cloud Tenant ID")
+    nhn_username = models.EmailField(blank=True, null=True, verbose_name="NHN Cloud Username")
+    encrypted_nhn_api_password = models.BinaryField(blank=True, null=True, verbose_name="NHN Cloud API Password (암호화)")
+    nhn_storage_account = models.CharField(max_length=128, blank=True, null=True, verbose_name="NHN Cloud Storage Account")
+
     objects = CustomUserManager()
 
     USERNAME_FIELD = 'email'
@@ -112,3 +118,27 @@ class CustomUser(AbstractBaseUser, PermissionsMixin):
         """
         self.encrypted_private_key = self.encrypt_private_key(private_key)
         self.save()
+
+    # ☁️ NHN Cloud API Password 암복호화
+    def encrypt_nhn_password(self, password: str) -> bytes:
+        """NHN Cloud API 비밀번호 암호화"""
+        cipher = Fernet(self.get_encryption_key())
+        return cipher.encrypt(password.encode())
+
+    def decrypt_nhn_password(self) -> str:
+        """NHN Cloud API 비밀번호 복호화"""
+        if self.encrypted_nhn_api_password:
+            cipher = Fernet(self.get_encryption_key())
+            return cipher.decrypt(self.encrypted_nhn_api_password).decode()
+        return ""
+
+    def save_nhn_credentials(self, tenant_id: str, username: str, password: str, storage_account: str = None):
+        """NHN Cloud 자격증명 저장"""
+        self.nhn_tenant_id = tenant_id
+        self.nhn_username = username
+        self.encrypted_nhn_api_password = self.encrypt_nhn_password(password)
+        if storage_account:
+            self.nhn_storage_account = storage_account
+        self.save(update_fields=[
+            'nhn_tenant_id', 'nhn_username', 'encrypted_nhn_api_password', 'nhn_storage_account'
+        ])