Add hand-end scoring summary screen with acknowledgement

After each hand of an unfinished match the game now pauses in a new
hand_end phase instead of dealing immediately:

- engine: hand_points gains an 'award' map (which team won each category),
  _end_hand stops at hand_end with a deadline, new acknowledge_hand deals
  the next hand once all four players have acked; plays are rejected while
  the summary is up
- state: acked seats, hand_end_deadline and hand_ack_timeout are persisted
  and exposed in the personalized view (also on the finished state, so the
  final hand is explained before the result)
- ws: new {"action": "ack"}; a per-hand timer force-deals the next hand
  after HAND_ACK_TIMEOUT_SECONDS (new env var, default 30s) so an away
  player cannot stall the match
- web: modal explaining each category in plain language with icons (card
  images for denara/settebello/primiera), team-coloured rows, running
  totals with progress bars, an 'Understood — next hand' button that turns
  into 'Waiting for …' plus an auto-continue countdown; the final screen
  shows the last hand's breakdown too

Verified in the browser against the compose stack: hand played to
completion, summary rendered (including a carte tie), ack from all four
players dealt the next hand live, and the auto-continue path fired when
nobody acked. 60 backend tests + mypy + cargo tests green.

server/src/scopa/routes/games.py

@@ -18,6 +18,7 @@ from kaya.openapi import operation
 from .. import auth
 from ..app import app, game_store, oidc_mixin
 from ..auth import require_auth
+from ..config import settings
 from ..game import engine
 from ..game.errors import GameError
 from ..game.state import DEFAULT_TARGET_SCORE, PHASE_LOBBY, GameState
@@ -103,6 +104,7 @@ async def create_game(ctx: HttpContext) -> None:
             creator_sub=user.sub,
             creator_name=auth.display_name(user),
             target_score=target_score,
+            hand_ack_timeout=settings.hand_ack_timeout_seconds,
         )
     except GameError as exc:
         await send_error(ctx, 400, str(exc))