Add configurable admin password via environment variable

- Add ORCHARD_ADMIN_PASSWORD env var to set initial admin password
- When set, admin user created without forced password change
- Add AWS Secrets Manager support for stage/prod deployments
- Add .env file support for local docker development
- Add Helm chart auth config (adminPassword, existingSecret, secretsManager)

Environments configured:
- Local: .env file or defaults to changeme123
- Feature/dev: orchardtest123 (hardcoded in values-dev.yaml)
- Stage: AWS Secrets Manager (orchard-stage-creds)
- Prod: AWS Secrets Manager (orch-prod-creds)

backend/tests/unit/test_auth.py

@@ -0,0 +1,95 @@
+"""Unit tests for authentication module."""
+
+import pytest
+from unittest.mock import patch, MagicMock
+
+
+class TestCreateDefaultAdmin:
+    """Tests for the create_default_admin function."""
+
+    def test_create_default_admin_with_env_password(self):
+        """Test that ORCHARD_ADMIN_PASSWORD env var sets admin password."""
+        from app.auth import create_default_admin, verify_password
+
+        # Create mock settings with custom password
+        mock_settings = MagicMock()
+        mock_settings.admin_password = "my-custom-password-123"
+
+        # Mock database session
+        mock_db = MagicMock()
+        mock_db.query.return_value.count.return_value = 0  # No existing users
+
+        # Track the user that gets created
+        created_user = None
+
+        def capture_user(user):
+            nonlocal created_user
+            created_user = user
+
+        mock_db.add.side_effect = capture_user
+
+        with patch("app.auth.get_settings", return_value=mock_settings):
+            admin = create_default_admin(mock_db)
+
+        # Verify the user was created
+        assert mock_db.add.called
+        assert created_user is not None
+        assert created_user.username == "admin"
+        assert created_user.is_admin is True
+        # Password should NOT require change when set via env var
+        assert created_user.must_change_password is False
+        # Verify password was hashed correctly
+        assert verify_password("my-custom-password-123", created_user.password_hash)
+
+    def test_create_default_admin_with_default_password(self):
+        """Test that default password 'changeme123' is used when env var not set."""
+        from app.auth import create_default_admin, verify_password
+
+        # Create mock settings with empty password (default)
+        mock_settings = MagicMock()
+        mock_settings.admin_password = ""
+
+        # Mock database session
+        mock_db = MagicMock()
+        mock_db.query.return_value.count.return_value = 0  # No existing users
+
+        # Track the user that gets created
+        created_user = None
+
+        def capture_user(user):
+            nonlocal created_user
+            created_user = user
+
+        mock_db.add.side_effect = capture_user
+
+        with patch("app.auth.get_settings", return_value=mock_settings):
+            admin = create_default_admin(mock_db)
+
+        # Verify the user was created
+        assert mock_db.add.called
+        assert created_user is not None
+        assert created_user.username == "admin"
+        assert created_user.is_admin is True
+        # Password SHOULD require change when using default
+        assert created_user.must_change_password is True
+        # Verify default password was used
+        assert verify_password("changeme123", created_user.password_hash)
+
+    def test_create_default_admin_skips_when_users_exist(self):
+        """Test that no admin is created when users already exist."""
+        from app.auth import create_default_admin
+
+        # Create mock settings
+        mock_settings = MagicMock()
+        mock_settings.admin_password = "some-password"
+
+        # Mock database session with existing users
+        mock_db = MagicMock()
+        mock_db.query.return_value.count.return_value = 1  # Users exist
+
+        with patch("app.auth.get_settings", return_value=mock_settings):
+            result = create_default_admin(mock_db)
+
+        # Should return None and not create any user
+        assert result is None
+        assert not mock_db.add.called