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/migrations/0009_add_nhn_cloud_credentials.py

@@ -0,0 +1,33 @@
+# Generated by Django 4.2.14 on 2026-01-13 15:05
+
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('users', '0008_add_unique_name'),
+    ]
+
+    operations = [
+        migrations.AddField(
+            model_name='customuser',
+            name='encrypted_nhn_api_password',
+            field=models.BinaryField(blank=True, null=True, verbose_name='NHN Cloud API Password (암호화)'),
+        ),
+        migrations.AddField(
+            model_name='customuser',
+            name='nhn_storage_account',
+            field=models.CharField(blank=True, max_length=128, null=True, verbose_name='NHN Cloud Storage Account'),
+        ),
+        migrations.AddField(
+            model_name='customuser',
+            name='nhn_tenant_id',
+            field=models.CharField(blank=True, max_length=64, null=True, verbose_name='NHN Cloud Tenant ID'),
+        ),
+        migrations.AddField(
+            model_name='customuser',
+            name='nhn_username',
+            field=models.EmailField(blank=True, max_length=254, null=True, verbose_name='NHN Cloud Username'),
+        ),
+    ]