Split backend into tavolo-platform, tavolo-scopone and tavolo-app packages

Move the game-independent machinery (lobby, live-game store, websocket,
deadline scheduler, match history, leaderboards) into a new
tavolo-platform distribution behind a GameEngine contract, the scopone
scientifico rules plus a platform adapter into tavolo-scopone, and keep
only the composition root in tavolo-app. The three distributions share
the tavolo namespace (PEP 420, kaya-style monorepo).

Match history becomes fully generic: Match carries the engine's result
JSON and MatchPlayer points/details instead of scopone-shaped team
columns (migration 3 backfills existing rows). Lobby creation takes an
opaque per-game options object and websocket actions dispatch to the
session's engine.

Tests: platform suite runs against a DummyEngine toy game, scopone
keeps the rules tests plus new adapter tests, server/tests covers the
wired stack end to end (194 tests, was 143).

server/packages/tavolo-platform/pyproject.toml

@@ -0,0 +1,38 @@
+[build-system]
+requires = ["setuptools>=68"]
+build-backend = "setuptools.build_meta"
+
+[project]
+name = "tavolo-platform"
+version = "0.1.0"
+description = "Game-independent multiplayer game platform (lobby, live play, match history, leaderboards) built on the kaya framework"
+readme = "README.md"
+requires-python = ">=3.10"
+dependencies = [
+    "kaya-core",
+    "kaya-session",
+    "kaya-oidc",
+    "kaya-openapi",
+    "tortoise-orm",
+    "redis",
+]
+
+[tool.setuptools.packages.find]
+where = ["src"]
+namespaces = true
+
+[tool.mypy]
+python_version = "3.12"
+ignore_missing_imports = true
+plugins = []
+
+# TortoiseORM auto-generates `<fk>_id` attributes on ForeignKeyField at
+# runtime; without the (unavailable here) tortoise mypy plugin the stubs
+# only declare the relation field. These are real attributes, not bugs.
+[[tool.mypy.overrides]]
+module = "tavolo.platform.models"
+disable_error_code = ["attr-defined"]
+
+[[tool.mypy.overrides]]
+module = "tavolo.platform.routes.*"
+disable_error_code = ["attr-defined"]