refactor: remove legacy user registration from auth_service

- Remove unused register_user() method and helper methods
- Remove legacy UserRegister schema (customer registration uses CustomerService)
- Remove wrapper methods that just delegated to auth_manager
- Simplify auth_service to focus on login and vendor access control
- Clean up tests to match simplified service

The only registration path is now /api/v1/shop/auth/register for customers,
which uses CustomerService.register_customer().

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

tests/unit/models/schema/test_auth.py

@@ -6,101 +6,11 @@ from pydantic import ValidationError
 from models.schema.auth import (
     UserCreate,
     UserLogin,
-    UserRegister,
     UserResponse,
     UserUpdate,
 )
 
 
-@pytest.mark.unit
-@pytest.mark.schema
-class TestUserRegisterSchema:
-    """Test UserRegister schema validation."""
-
-    def test_valid_registration(self):
-        """Test valid registration data."""
-        user = UserRegister(
-            email="test@example.com",
-            username="testuser",
-            password="password123",
-        )
-        assert user.email == "test@example.com"
-        assert user.username == "testuser"
-        assert user.password == "password123"
-
-    def test_username_normalized_to_lowercase(self):
-        """Test username is normalized to lowercase."""
-        user = UserRegister(
-            email="test@example.com",
-            username="TestUser",
-            password="password123",
-        )
-        assert user.username == "testuser"
-
-    def test_username_with_whitespace_invalid(self):
-        """Test username with whitespace is invalid (validation before strip)."""
-        with pytest.raises(ValidationError) as exc_info:
-            UserRegister(
-                email="test@example.com",
-                username="  testuser  ",
-                password="password123",
-            )
-        assert "username" in str(exc_info.value).lower()
-
-    def test_invalid_email(self):
-        """Test invalid email raises ValidationError."""
-        with pytest.raises(ValidationError) as exc_info:
-            UserRegister(
-                email="not-an-email",
-                username="testuser",
-                password="password123",
-            )
-        assert "email" in str(exc_info.value).lower()
-
-    def test_invalid_username_special_chars(self):
-        """Test username with special characters raises ValidationError."""
-        with pytest.raises(ValidationError) as exc_info:
-            UserRegister(
-                email="test@example.com",
-                username="test@user!",
-                password="password123",
-            )
-        assert "username" in str(exc_info.value).lower()
-
-    def test_valid_username_with_underscore(self):
-        """Test username with underscore is valid."""
-        user = UserRegister(
-            email="test@example.com",
-            username="test_user_123",
-            password="password123",
-        )
-        assert user.username == "test_user_123"
-
-    def test_password_too_short(self):
-        """Test password shorter than 6 characters raises ValidationError."""
-        with pytest.raises(ValidationError) as exc_info:
-            UserRegister(
-                email="test@example.com",
-                username="testuser",
-                password="12345",
-            )
-        assert "password" in str(exc_info.value).lower()
-
-    def test_password_exactly_6_chars(self):
-        """Test password with exactly 6 characters is valid."""
-        user = UserRegister(
-            email="test@example.com",
-            username="testuser",
-            password="123456",
-        )
-        assert user.password == "123456"
-
-    def test_missing_required_fields(self):
-        """Test missing required fields raises ValidationError."""
-        with pytest.raises(ValidationError):
-            UserRegister(email="test@example.com")
-
-
 @pytest.mark.unit
 @pytest.mark.schema
 class TestUserLoginSchema: