fix: drop game_number by one for finished playoff cards

Scoreboard payloads don't include gameNumber, so the previous fix fell straight through to series_state['game_number'], which is hi+lo+1 — the *next* game. Once a game goes FINAL the win for this game is already banked in seriesStatus, so the card's own number is hi+lo. For the just-played Game 1 of Kings/Avalanche (series now 1-0), this brings the header back to "Game 1 of 7" instead of "Game 2 of 7".

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

app/playoff.py

@@ -93,11 +93,16 @@ def series_state(series_status):
 
 
 def _game_number(game, state):
-    """This card's game number. Prefer the raw ``gameNumber`` field so we don't
-    drift forward once ``seriesStatus`` advances after the game ends."""
+    """This card's game number. seriesStatus counts wins through the current
+    payload, so once a game goes FINAL the win for this game is already banked
+    and state['game_number'] (hi+lo+1) points at the *next* game. For a finished
+    card, pin to hi+lo. The scoreboard payload doesn't carry a raw gameNumber,
+    but we honor it if present (e.g. from the series-detail endpoint)."""
     raw = game.get("gameNumber")
     if isinstance(raw, int) and raw > 0:
         return raw
+    if game.get("gameState") in ("FINAL", "OFF"):
+        return max(1, state["hi"] + state["lo"])
     return state["game_number"]