Document every API response body in the OpenAPI spec

kaya-openapi 0.0.8 supports named component schemas, so the routes'
description-only responses become $refs: schemas for the core payloads
(auth providers, lobby, game view, ongoing games, match history,
leaderboard, ratings) live in tavolo.platform.openapi and are registered
through the mixin's components. Engine-defined parts (options echo, game
views, match results) stay open objects on purpose. Error responses now
carry the error envelope schema, and a new suite sweeps the document to
keep every /api response typed.

server/requirements.txt

@@ -79,7 +79,7 @@ kaya-cors==0.0.7
     # via tavolo-app (pyproject.toml)
 kaya-oidc==0.0.7
     # via tavolo-app (pyproject.toml)
-kaya-openapi==0.0.7
+kaya-openapi==0.0.8
     # via tavolo-app (pyproject.toml)
 kaya-otel==0.0.7
     # via tavolo-app (pyproject.toml)