feat: add support for user registration toggle and Traefik integration in Docker setup

k-tv-backend/api/src/routes/auth.rs

@@ -73,6 +73,10 @@ async fn register(
     State(state): State<AppState>,
     Json(payload): Json<RegisterRequest>,
 ) -> Result<impl IntoResponse, ApiError> {
+    if !state.config.allow_registration {
+        return Err(ApiError::Forbidden("Registration is disabled".to_string()));
+    }
+
     let password_hash = infra::auth::hash_password(payload.password.as_ref());
 
     let user = state