Show full playoff bracket, mark series results, harden API decoding

Playoffs:
- List every round played so far (Round 1 → current) instead of only the
  current round, on both macOS menu and iPhone
- Strike through the eliminated team's tricode in a finished series and drop
  the now-redundant "(Final … wins)" tag on completed earlier rounds
- Refetch the bracket when a finished game implies more completed games than
  the cached bracket records, so the series score and round no longer get
  stuck on stale data after cold launch or the NHL bracket endpoint's lag

API robustness:
- Tolerate optional gameCenterLink/startTimeUTC on TBD playoff matchups so the
  scoreboard decode no longer aborts
- Reject API state regressions via a monotonic FUT→…→OFF progression rank so a
  brief glitch can't downgrade a finished game back to "-:-"

Shared/Models/ScoreboardModel.swift

@@ -26,8 +26,10 @@ struct Scoreboard: Codable {
         let season: Int
         let gameType: Int
         let gameDate: String
-        let gameCenterLink: String
-        let startTimeUTC: String
+        /// Missing on TBD playoff matchups (opponent not yet decided).
+        let gameCenterLink: String?
+        /// Missing on TBD playoff matchups not yet scheduled.
+        let startTimeUTC: String?
         let gameState: String
         let gameScheduleState: String
         let awayTeam: Team
@@ -62,19 +64,23 @@ struct Scoreboard: Codable {
         }
 
         var date: Date {
-            ISO8601DateFormatter().date(from: startTimeUTC) ?? .now
+            guard let startTimeUTC else { return .distantFuture }
+            return ISO8601DateFormatter().date(from: startTimeUTC) ?? .now
         }
 
-        var gameCenterUrl: String {
-            "https://www.nhl.com\(gameCenterLink)"
+        var gameCenterUrl: String? {
+            guard let gameCenterLink else { return nil }
+            return "https://www.nhl.com\(gameCenterLink)"
         }
 
         var videocastUrl: String {
             "https://videocast.nhl.com/game/\(id)/usnded?autoplay=true"
         }
 
-        /// Time string in ET, right-aligned to 8 chars (e.g. " 9:30 PM", "10:00 PM")
+        /// Time string in ET, right-aligned to 8 chars (e.g. " 9:30 PM", "10:00 PM").
+        /// Empty when the game has no scheduled start (TBD opponent).
         var startTimeET: String {
+            guard startTimeUTC != nil else { return "" }
             let raw = date.formatDateET(format: "h:mm a")
             return raw.count < 8
                 ? String(repeating: " ", count: 8 - raw.count) + raw