Get the signed-in user profile and their activity totals

Carries memberSince, which GET /auth/user cannot: that route returns the entity, whose created_at is excluded from serialization.

curl -X GET "http://localhost:8000/api/auth/user/profile" \
  -H "Authorization: Bearer YOUR_TOKEN"

const response = await fetch("http://localhost:8000/api/auth/user/profile", {
  method: "GET",
  headers: {
    "Authorization": "Bearer YOUR_TOKEN"
  }
});