fix(phase-4): close review notes — drop dead var, sync UI cron default

Phase 4 reviewer (Sonnet) flagged two 🟡 warnings; both addressed:

1. PullLiveOddsUseCase: removed dead 'liveEvents' assignment that called
   ScrapeUpcomingAsync but never read the result. Replaced misleading
   comment block with a single TODO(phase-6/8) note pointing to the
   ListLiveAsync(cutoff) follow-up.
2. Marathon.UI.Services.WorkerOptions.UpcomingScheduleCron: changed default
   from '0 */5 * * * *' (every 5 min) to '0 0 */6 * * *' (every 6 hours)
   to match Marathon.Infrastructure.Configuration.WorkerOptions and the
   appsettings.json default.

PLAN.md: Phase 4 row updated (review status, commit hash); top-level
checkbox in Phases list ticked.

Build 0/0, all 202 tests still passing.

src/Marathon.Application/UseCases/PullLiveOddsUseCase.cs

@@ -36,13 +36,11 @@ public sealed class PullLiveOddsUseCase
     {
         _logger.LogInformation("PullLiveOddsUseCase: cycle started");
 
-        // Fetch live events from scraper — returns only events currently live on site.
-        var liveEvents = await _scraper.ScrapeUpcomingAsync(sportFilter: null, ct);
-
-        // Note: the scraper's ScrapeUpcomingAsync returns pre-match by default.
-        // For the live cycle, we load known events from the DB and refresh each one.
-        // The "live vs pre-match" distinction is handled by OddsSource.Live in the snapshot.
-        // We use the DB list because the site's live listing may differ from what we track.
+        // Refresh odds for every event we already track. The "live vs pre-match"
+        // distinction is recorded by stamping each snapshot with OddsSource.Live.
+        // TODO(phase-6/8): once IEventRepository.ListLiveAsync(cutoff) ships, swap
+        // this for a filter that only returns currently-live events to avoid
+        // hammering the scraper with non-live IDs.
         var allEvents = await _eventRepo.ListAsync(ct);
 
         int snapshotsCaptured = 0;

src/Marathon.UI/Services/WorkerOptions.cs

@@ -9,7 +9,7 @@ public sealed class WorkerOptions
     public const string SectionName = "Workers";
 
     /// <summary>Cron expression that drives the upcoming-schedule poller.</summary>
-    public string UpcomingScheduleCron { get; set; } = "0 */5 * * * *";
+    public string UpcomingScheduleCron { get; set; } = "0 0 */6 * * *";
 
     /// <summary>Whether the live odds poller should run at startup.</summary>
     public bool LivePollerEnabled { get; set; } = true;