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>

app/bracket_view.py

@@ -0,0 +1,132 @@
+"""Normalize NHL /v1/playoff-bracket payloads for the bracket template.
+
+The NHL bracket uses stable series letters:
+  A,B,C,D = Round 1 East    E,F,G,H = Round 1 West
+  I,J     = Round 2 East    K,L     = Round 2 West
+  M       = Conf Final East N       = Conf Final West
+  O       = Stanley Cup Final
+"""
+
+from app.playoff import ROUND_LABELS
+
+EAST_R1 = ["A", "B", "C", "D"]
+WEST_R1 = ["E", "F", "G", "H"]
+EAST_R2 = ["I", "J"]
+WEST_R2 = ["K", "L"]
+EAST_CF = ["M"]
+WEST_CF = ["N"]
+CUP_FINAL = ["O"]
+
+
+def build_bracket_view(year, bracket_payload, fetched_at=None):
+    """Shape the raw bracket API payload for bracket.html.
+
+    Returns a dict of rounds grouped by conference, plus a flat `matchups` list
+    keyed by letter for the mobile accordion. Missing letters render as empty
+    placeholder slots so the grid stays visually complete before upsets decide.
+    """
+    series_by_letter = {}
+    for s in (bracket_payload or {}).get("series", []):
+        letter = s.get("seriesLetter")
+        if letter:
+            series_by_letter[letter] = s
+
+    def slot(letter):
+        return _matchup(year, letter, series_by_letter.get(letter))
+
+    east_r1 = [slot(l) for l in EAST_R1]
+    west_r1 = [slot(l) for l in WEST_R1]
+    east_r2 = [slot(l) for l in EAST_R2]
+    west_r2 = [slot(l) for l in WEST_R2]
+    east_cf = [slot(l) for l in EAST_CF]
+    west_cf = [slot(l) for l in WEST_CF]
+    cup = [slot(l) for l in CUP_FINAL]
+
+    return {
+        "year": year,
+        "fetched_at": fetched_at,
+        "bracket_logo": (bracket_payload or {}).get("bracketLogo"),
+        "east_r1": east_r1,
+        "west_r1": west_r1,
+        "east_r2": east_r2,
+        "west_r2": west_r2,
+        "east_cf": east_cf,
+        "west_cf": west_cf,
+        "cup": cup,
+        "rounds": [
+            {"label": ROUND_LABELS[1], "east": east_r1, "west": west_r1},
+            {"label": ROUND_LABELS[2], "east": east_r2, "west": west_r2},
+            {"label": ROUND_LABELS[3], "east": east_cf, "west": west_cf},
+            {"label": ROUND_LABELS[4], "cup": cup},
+        ],
+    }
+
+
+def _matchup(year, letter, series):
+    """Render-ready dict for one bracket slot. Empty when the series is unknown."""
+    if not series:
+        return {
+            "letter": letter,
+            "series_id": f"{year}-{letter}",
+            "empty": True,
+            "top": None,
+            "bottom": None,
+            "top_wins": 0,
+            "bottom_wins": 0,
+            "round": None,
+            "winner_abbrev": None,
+            "state": "pending",
+        }
+
+    top = series.get("topSeedTeam") or {}
+    bot = series.get("bottomSeedTeam") or {}
+    top_wins = _to_int(series.get("topSeedWins"))
+    bot_wins = _to_int(series.get("bottomSeedWins"))
+    winning_id = series.get("winningTeamId")
+
+    winner_abbrev = None
+    if winning_id is not None:
+        if top.get("id") == winning_id:
+            winner_abbrev = top.get("abbrev")
+        elif bot.get("id") == winning_id:
+            winner_abbrev = bot.get("abbrev")
+
+    if winner_abbrev:
+        state = "complete"
+    elif top_wins > 0 or bot_wins > 0:
+        state = "active"
+    else:
+        state = "upcoming"
+
+    return {
+        "letter": letter,
+        "series_id": f"{year}-{letter}",
+        "empty": False,
+        "top": _team(top, series.get("topSeedRankAbbrev")),
+        "bottom": _team(bot, series.get("bottomSeedRankAbbrev")),
+        "top_wins": top_wins,
+        "bottom_wins": bot_wins,
+        "round": series.get("playoffRound"),
+        "winner_abbrev": winner_abbrev,
+        "state": state,
+    }
+
+
+def _team(team, seed_abbrev=None):
+    if not team:
+        return None
+    return {
+        "id": team.get("id"),
+        "abbrev": team.get("abbrev"),
+        "name": (team.get("name") or {}).get("default"),
+        "common_name": (team.get("commonName") or {}).get("default"),
+        "logo": team.get("darkLogo") or team.get("logo"),
+        "seed": seed_abbrev,
+    }
+
+
+def _to_int(v, default=0):
+    try:
+        return int(v)
+    except (TypeError, ValueError):
+        return default