feat(api): login and authentication routes

- Remove fastapi-limiter, we will rate limit at load balancer level as
it is too hard to get fastapi-limiter to play nice with pytest.
- Wrote technical writeups on how the login flow and check for user
authentication status work

backend/tests/test_route_member.py

@@ -0,0 +1,10 @@
+from fastapi.testclient import TestClient
+
+from src.neo_neo_todo.main import app
+
+
+async def test_get_current_member():
+    with TestClient(app) as client:
+        response = client.get("/members/me")
+        assert response.status_code == 401
+        assert response.json() == {"detail": "Not authenticated"}