Add briscola: classic two-player and briscola a quattro

New tavolo-briscola distribution implementing briscola on the platform:

- pure rules (state.py, engine.py): 3-card deals, a face-up trump that
  is the last card drawn, trump-first trick resolution (A > 3 > K > H >
  J > 7 > 6 > 5 > 4 > 2), 120 points per deal, 60-60 patta re-deals, a
  configurable target score (default 61), deal-end acknowledgements and
  turn auto-play;
- BriscolaEngine (briscola, 2 players) and BriscolaQuattroEngine
  (briscola_a_quattro, 4 players in fixed partnerships) adapters;
- registered in tavolo-app, packaged in the Docker image, documented.

Platform fixes surfaced by a two-player lobby:

- the websocket state and snapshot payloads now carry seats_open (they
  were only in the REST lobby payload), so lobbies with player counts
  other than four render correctly; seats_open is clamped at zero;
- the web client logs unparseable server messages instead of silently
  dropping them.

Web client: briscola table for both variants (stock, face-up trump,
trick, last-trick banner), deal summary modal and game-over overlay.

Tests: tavolo-briscola rules/adapter suites, app integration tests
(lobby, websocket play, turn timeout, deal-end acks, persistence), a
platform seats_open test and frontend model parsing tests.

server/tests/test_stats.py

@@ -136,5 +136,91 @@ class ScoponeStatsTest(unittest.TestCase):
             self.assertTrue(all(r["matches"] == 1 for r in by_sub.values()))
 
 
+async def _finished_briscola_session() -> GameSession:
+    engine = platform.registry.require("briscola")
+    session = GameSession(
+        id="stats-briscola-1",
+        game_type=engine.id,
+        join_code="BS0001",
+        creator_sub="alice",
+        players=[Seat(user_sub="alice", display_name="Alice")],
+    )
+    engine.create(session, {})
+    engine.join(session, "bob", "Bob")
+    moves = 0
+    while not engine.is_finished(session) and moves < 200000:
+        state = session.state
+        if state.phase == "hand_end":
+            for player in state.players:
+                engine.handle_action(session, player.sub, "ack", {})
+            continue
+        player = next(p for p in state.players if p.seat == state.turn)
+        engine.handle_action(
+            session, player.sub, "play", {"card": player.hand[0].code}
+        )
+        moves += 1
+    assert engine.is_finished(session)
+    return session
+
+
+class BriscolaStatsTest(unittest.TestCase):
+    @async_test
+    async def test_finished_briscola_match_persisted_with_summary(self) -> None:
+        await tortoise_mixin._bind()
+        ctx = tortoise_mixin._ctx
+        assert ctx is not None
+        engine = platform.registry.require("briscola")
+        session = await _finished_briscola_session()
+        with ctx:
+            await save_match_result(session, engine)
+            self.assertEqual(1, await Match.all().count())
+            self.assertEqual(2, await MatchPlayer.all().count())
+
+            match = await Match.all().first()
+            assert match is not None
+            self.assertEqual("briscola", match.game_type)
+            summary = match.result
+            self.assertIn("team_a_score", summary)
+            self.assertIn("team_b_score", summary)
+            self.assertIn("winner_team", summary)
+            self.assertIn("target_score", summary)
+            self.assertIn("deals_played", summary)
+            self.assertIn("deal_scores", summary)
+
+            winner_team = summary["winner_team"]
+            players = {p.user_sub: p for p in await MatchPlayer.all()}
+            for row in players.values():
+                if row.won:
+                    self.assertEqual(winner_team, row.team)
+                else:
+                    self.assertNotEqual(winner_team, row.team)
+            # A two-player match moves Elo by 16 points each.
+            ratings = {r.user_sub: r.rating for r in await PlayerRating.all()}
+            self.assertEqual(2, len(ratings))
+            self.assertEqual(
+                {INITIAL_RATING + 16, INITIAL_RATING - 16}, set(ratings.values())
+            )
+
+    @async_test
+    async def test_history_exposes_briscola_result(self) -> None:
+        await tortoise_mixin._bind()
+        ctx = tortoise_mixin._ctx
+        assert ctx is not None
+        engine = platform.registry.require("briscola")
+        session = await _finished_briscola_session()
+        with ctx:
+            await save_match_result(session, engine)
+        transport = ASGITransport(app=app)
+        async with AsyncClient(transport=transport, base_url="http://127.0.0.1") as client:
+            with oidc_user("alice"):
+                history = await client.get("/api/me/matches")
+            self.assertEqual(200, history.status_code)
+            results = history.json()["results"]
+            self.assertEqual(1, len(results))
+            self.assertEqual("briscola", results[0]["game_type"])
+            self.assertIn("team_a_score", results[0]["result"])
+            self.assertEqual(2, len(results[0]["players"]))
+
+
 if __name__ == "__main__":
     unittest.main()