Initial scopone scientifico backend

Multiplayer scopone scientifico backend on the kaya framework:

- OIDC login (kaya-oidc), session-backed WebSocket auth
- Pure rules engine (forced captures, scopa, primiera scoring) with
  full-match simulation tests
- Live game state in Redis (JSON + TTL, join codes, per-game locks,
  pub/sub state push); in-memory fallback for tests
- WebSocket /ws/games/{id} for real-time play; REST lobby endpoints
  (create/join/snapshot) with hidden-hand views
- Finished matches persisted to Postgres (Tortoise + aerich) for match
  history and leaderboard endpoints
- Docker Compose stack: postgres, redis, mock-oauth2-server, db-migrate, app
- 45 tests passing; mypy clean

.env.example

@@ -0,0 +1,25 @@
+# Postgres
+POSTGRES_HOST=localhost
+POSTGRES_PORT=5432
+POSTGRES_DB=scopa
+POSTGRES_USER=scopa
+POSTGRES_PASSWORD=scopa
+DATABASE_URL=postgres://scopa:scopa@localhost:5432/scopa
+
+# OIDC (mock-oauth2-server in dev; it does not validate clients, so any
+# client id/secret works. For a real IdP like Keycloak, use its values here.)
+OIDC_ISSUER=http://localhost:8180/scopa
+OIDC_CLIENT_ID=scopa
+OIDC_CLIENT_SECRET=dev-secret
+OIDC_REDIRECT_URI=http://localhost:8080/auth/callback
+
+# Redis (session and live-game storage). Unset to fall back to in-memory
+# stores (only sensible for local development with a single worker).
+REDIS_URL=redis://localhost:6379/0
+
+# How long a live game survives in Redis without activity.
+GAME_TTL_SECONDS=86400
+
+# App server
+APP_HOST=0.0.0.0
+APP_PORT=8080