Add scopa: classic two-player and scopa a quattro

New tavolo-scopa package with a pure rules engine and the platform
adapters for two-player scopa and four-player fixed-partnership scopa a
quattro: three cards each and four on the table, capture by rank or sum,
sweep for scope and score carte/denara/settebello/primiera.

The optional asso pigliatutto creation option turns either variant into
scopa d'assi (an ace sweeps the whole table and scores no scopa), reusing
scopone's rule semantics.

Wire both engines into the app and the Docker install, add the scopa
table view to the SPA (duo and four-seat layouts, deck count,
captured/scope stats, hand-summary and final screens, player names in the
two-player summary), and cover the rules, the platform contract, the
REST/WebSocket flows, match persistence and Elo.

web/src/pages/lobby.rs

@@ -514,7 +514,7 @@ pub fn LobbyPage() -> View {
                             div(class="lobby-hero text-center") {
                                 h1(class="display-5 fw-bold") { "tavolo" }
                                 p(class="lead text-secondary mb-0") {
-                                    "Play scopone scientifico and briscola with friends."
+                                    "Play scopone, scopa and briscola with friends."
                                 }
                             }
                             // Ongoing games: a "Continue" link back into a