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/app/modules/notifications/service.py

@@ -0,0 +1,8 @@
+"""Celery-ready notifications service placeholder.
+
+MVP keeps SMTP sync path in auth; v1.0 should move to async queue.
+"""
+
+
+def enqueue_email(template: str, recipient: str, context: dict) -> dict:
+    return {"queued": True, "template": template, "recipient": recipient, "context": context}