feat: make scoreboard playoff-aware with banner, bracket, and series drill-down

Turn a regular-season-looking Tuesday into a full playoff experience:

- Playoff banner with round + day + series + elimination counts, gold/silver
  Cup theme toggled by body.playoff-mode
- Series context on each playoff card: round chip, series score, stake badges
  (GAME 7, CLINCHER, PIVOTAL), and one-line blurb
- Game 7s pin to a new Spotlight section above Live
- Playoff OT renders with SUDDEN DEATH badge and pulsing gold border
- Client-side OT notifications via bell button in the banner
- New /series/<id> drill-down with headline, next-game, and game-by-game history
- New /bracket page: 7-column desktop grid, accordion on mobile
- Day N banner count auto-anchors on first playoff scoreboard hit
- SQLite cache for bracket + per-series schedules, stale-on-failure up to 24h

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

tests/test_games.py

@@ -1,5 +1,5 @@
 import app.games
-from tests.conftest import make_game
+from tests.conftest import make_game, make_playoff_game
 from app.games import (
     _get_man_advantage,
     calculate_game_importance,
@@ -745,6 +745,107 @@ class TestGetComebackBonus:
         assert result == 70  # 50*1.0 + 20
 
 
+class TestPlayoffEnrichment:
+    _FULL_STANDINGS = {
+        "league_sequence": 16,
+        "league_l10_sequence": 16,
+        "division_abbrev": "ATL",
+        "conference_abbrev": "E",
+        "games_played": 40,
+        "wildcard_sequence": 16,
+    }
+
+    def test_regular_season_game_has_empty_playoff_fields(self, mocker):
+        mocker.patch(
+            "app.games.get_team_standings", return_value=self._FULL_STANDINGS
+        )
+        result = parse_games({"games": [make_game()]})
+        g = result[0]
+        assert g["Is Playoff"] is False
+        assert g["Pinned"] is False
+        assert g["Playoff OT"] is False
+        assert g["Series Blurb"] == ""
+        assert g["Series Badges"] == []
+
+    def test_playoff_game_gets_series_fields(self, mocker):
+        mocker.patch(
+            "app.games.get_team_standings",
+            return_value={"league_sequence": 0, "league_l10_sequence": 0},
+        )
+        game = make_playoff_game(top_wins=2, bottom_wins=1, round_num=1)
+        result = parse_games({"games": [game]})
+        g = result[0]
+        assert g["Is Playoff"] is True
+        assert g["Pinned"] is False
+        assert "Game 4" in g["Series Blurb"]
+        assert "R1" in g["Series Badges"]
+
+    def test_game7_is_pinned(self, mocker):
+        mocker.patch(
+            "app.games.get_team_standings",
+            return_value={"league_sequence": 0, "league_l10_sequence": 0},
+        )
+        game = make_playoff_game(top_wins=3, bottom_wins=3)
+        result = parse_games({"games": [game]})
+        assert result[0]["Pinned"] is True
+        assert "GAME 7" in result[0]["Series Badges"]
+
+    def test_pinned_game_sorts_first(self, mocker):
+        mocker.patch(
+            "app.games.get_team_standings", return_value=self._FULL_STANDINGS
+        )
+        # Low-priority Game 7 PRE should sort above a high-priority non-playoff LIVE
+        g7_pre = make_playoff_game(
+            top_wins=3,
+            bottom_wins=3,
+            game_state="FUT",
+            period=0,
+            seconds_remaining=1200,
+            start_time_utc="2026-04-20T23:00:00Z",
+            home_name="Kings",
+            away_name="Oilers",
+        )
+        hype_live = make_game(
+            game_state="LIVE",
+            home_name="Rangers",
+            away_name="Devils",
+            home_score=2,
+            away_score=2,
+            period=3,
+            seconds_remaining=60,
+        )
+        result = parse_games({"games": [hype_live, g7_pre]})
+        assert result[0]["Home Team"] == "Kings"
+        assert result[0]["Pinned"] is True
+
+    def test_playoff_ot_flagged(self, mocker):
+        mocker.patch(
+            "app.games.get_team_standings",
+            return_value={"league_sequence": 0, "league_l10_sequence": 0},
+        )
+        game = make_playoff_game(
+            top_wins=1,
+            bottom_wins=1,
+            period=4,
+            seconds_remaining=600,
+            game_state="LIVE",
+        )
+        result = parse_games({"games": [game]})
+        assert result[0]["Playoff OT"] is True
+        assert result[0]["OT Label"] == "OT"
+
+    def test_regular_season_ot_not_flagged_as_playoff_ot(self, mocker):
+        mocker.patch(
+            "app.games.get_team_standings", return_value=self._FULL_STANDINGS
+        )
+        game = make_game(
+            game_state="LIVE", period=4, seconds_remaining=180, game_type=2
+        )
+        result = parse_games({"games": [game]})
+        assert result[0]["Playoff OT"] is False
+        assert result[0]["OT Label"] == ""
+
+
 class TestCalculateGameImportance:
     def _standings(
         self,