Update admin theme/layout and refresh README details.

Align the project baseline with the latest admin interface styling and layout structure while documenting setup and usage updates in README.

apps/api/tests/modules/notifications/test_notifications_service.py

@@ -0,0 +1,7 @@
+from app.modules.notifications.service import enqueue_email
+
+
+def test_enqueue_email_returns_payload():
+    data = enqueue_email("verify", "u@example.com", {"token": "123"})
+    assert data["queued"] is True
+    assert data["template"] == "verify"