Introduce architettura multi-sport con catalogo, engine scoring e overlay.

Catalogo sport in YAML, board implicito, engine per volley/basket/timed/racket/timer/generic, regia e app Android allineate.

Co-authored-by: Cursor <cursoragent@cursor.com>

backend/config/routes.rb

@@ -10,6 +10,7 @@ Rails.application.routes.draw do
       post "auth/logout", to: "auth#logout"
       post "auth/refresh", to: "auth#refresh"
       get "auth/me", to: "auth#me"
+      get "sports", to: "sports#index"
 
       get "invitations/:token", to: "invitations#show"
       post "invitations/:token/accept", to: "invitations#accept"