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_routes_games.py

@@ -1,4 +1,4 @@
-"""Game lobby route tests via kaya's ASGI transport (scopone game)."""
+"""Game lobby route tests via kaya's ASGI transport (all registered games)."""
 from __future__ import annotations
 
 import unittest
@@ -253,16 +253,32 @@ class GameTypesRouteTest(unittest.TestCase):
             response = await client.get("/api/game-types")
         self.assertEqual(200, response.status_code)
         results = response.json()["results"]
-        self.assertEqual(["scopone_scientifico"], [g["id"] for g in results])
-        self.assertEqual("Scopone scientifico", results[0]["name"])
-        self.assertTrue(results[0]["description"])
-        self.assertEqual(4, results[0]["min_players"])
-        self.assertEqual(4, results[0]["max_players"])
-        self.assertIn("target_score", results[0]["options_schema"]["properties"])
-        self.assertIn("napola", results[0]["options_schema"]["properties"])
-        self.assertIn(
-            "asso_pigliatutto", results[0]["options_schema"]["properties"]
+        self.assertEqual(
+            ["scopone_scientifico", "briscola", "briscola_a_quattro"],
+            [g["id"] for g in results],
         )
+        scopone = results[0]
+        self.assertEqual("Scopone scientifico", scopone["name"])
+        self.assertTrue(scopone["description"])
+        self.assertEqual(4, scopone["min_players"])
+        self.assertEqual(4, scopone["max_players"])
+        self.assertIn("target_score", scopone["options_schema"]["properties"])
+        self.assertIn("napola", scopone["options_schema"]["properties"])
+        self.assertIn(
+            "asso_pigliatutto", scopone["options_schema"]["properties"]
+        )
+        briscola = results[1]
+        self.assertEqual("Briscola", briscola["name"])
+        self.assertTrue(briscola["description"])
+        self.assertEqual(2, briscola["min_players"])
+        self.assertEqual(2, briscola["max_players"])
+        self.assertIn("target_score", briscola["options_schema"]["properties"])
+        quattro = results[2]
+        self.assertEqual("Briscola a quattro", quattro["name"])
+        self.assertTrue(quattro["description"])
+        self.assertEqual(4, quattro["min_players"])
+        self.assertEqual(4, quattro["max_players"])
+        self.assertIn("target_score", quattro["options_schema"]["properties"])
 
     @async_test
     async def test_create_defaults_game_type(self) -> None:
@@ -294,7 +310,7 @@ class GameTypesRouteTest(unittest.TestCase):
         transport = ASGITransport(app=app)
         async with AsyncClient(transport=transport, base_url="http://127.0.0.1") as client:
             with oidc_user("alice"):
-                unknown = await client.post("/api/games", json={"game_type": "briscola"})
+                unknown = await client.post("/api/games", json={"game_type": "tresette"})
                 non_string = await client.post("/api/games", json={"game_type": 42})
             self.assertEqual(400, unknown.status_code)
             self.assertEqual(400, non_string.status_code)