Fix token request validation - accept any username format

- Change username field from EmailField to CharField in TokenRequestSerializer
- NHN Cloud API validates credentials, backend shouldn't restrict format
- Bump version to v0.0.2

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

nhn/serializers.py

@@ -17,8 +17,9 @@ class TokenRequestSerializer(serializers.Serializer):
         help_text="NHN Cloud 테넌트 ID",
         max_length=64,
     )
-    username = serializers.EmailField(
-        help_text="NHN Cloud 사용자 이메일",
+    username = serializers.CharField(
+        help_text="NHN Cloud 사용자 ID (이메일 또는 API 사용자 ID)",
+        max_length=255,
     )
     password = serializers.CharField(
         help_text="NHN Cloud API 비밀번호",