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/helpers.py

@@ -0,0 +1,30 @@
+from __future__ import annotations
+
+from fastapi.testclient import TestClient
+
+from app.core.email import memory_mailer
+
+
+def clear_sent_emails() -> None:
+    memory_mailer.clear()
+
+
+def latest_token(recipient: str, template: str) -> str:
+    token = memory_mailer.latest_token(recipient, template)
+    if not token:
+        raise AssertionError(f"No {template} email sent to {recipient}")
+    return token
+
+
+def register_and_verify(client: TestClient, email: str, password: str = "Valid123") -> None:
+    client.post("/api/v1/auth/register", json={"email": email, "password": password})
+    token = latest_token(email, "verify_email")
+    response = client.post("/api/v1/auth/verify-email", json={"token": token})
+    assert response.status_code == 200
+
+
+def register_verify_login(client: TestClient, email: str, password: str = "Valid123") -> dict[str, str]:
+    register_and_verify(client, email, password)
+    login = client.post("/api/v1/auth/login", json={"email": email, "password": password})
+    assert login.status_code == 200
+    return {"Authorization": f"Bearer {login.json()['access_token']}"}