feat(phase-4): application layer + background workers — 202/202 tests green

Use cases (Marathon.Application/UseCases/):
- PullUpcomingEventsUseCase: scrape + persist new events + capture pre-match snapshots
- PullLiveOddsUseCase: refresh live snapshots for all stored events
- PullResultsUseCase: Phase 4 scaffold; delegates to ScrapeResultsAsync (Phase 3 no-op);
  Phase 8 will replace with watch-list polling
- ExportToExcelUseCase: resolves export dir from StorageOptions, delegates to IExcelExporter

ApplicationModule.AddMarathonApplication(IServiceCollection) — no IConfiguration needed.

Background workers (Marathon.Infrastructure/Workers/):
- UpcomingEventsPoller: Cronos 6-field cron schedule (default every 6 h)
- LiveOddsPoller: fixed interval (WorkerOptions.LivePollIntervalSeconds, default 30 s)
- ResultsWatchListPoller: scaffold, disabled by default (WorkerOptions.ResultsPollerEnabled=false)
All three: exception-swallowing, cancellation-aware, scoped DI via CreateAsyncScope().

InfrastructureModule.AddMarathonInfrastructure(IServiceCollection, IConfiguration):
- Composes AddMarathonPersistence + AddMarathonScraping + WorkerOptions + 3 hosted services

App.xaml.cs: replace reflection-based TryAddApplicationAndInfrastructure with direct
AddMarathonApplication() + AddMarathonInfrastructure(config) calls.

Resolved Phase 3 TODO: bind Sports:Basketball:QuarterMode from config in ScrapingModule.

appsettings.json: add Workers.LivePollIntervalSeconds, ResultsPollIntervalSeconds,
ResultsPollerEnabled; add Sports.Basketball.QuarterMode.

Settings.razor + WorkerOptions (UI) + SharedResource.*.resx: surface new Workers fields.

Tests: +14 Application use-case tests, +3 Infrastructure worker tests (185 → 202 total).

src/Marathon.Infrastructure/InfrastructureModule.cs

@@ -0,0 +1,50 @@
+using Marathon.Infrastructure.Configuration;
+using Marathon.Infrastructure.Persistence;
+using Marathon.Infrastructure.Scraping;
+using Marathon.Infrastructure.Workers;
+using Microsoft.Extensions.Configuration;
+using Microsoft.Extensions.DependencyInjection;
+
+namespace Marathon.Infrastructure;
+
+/// <summary>
+/// Top-level DI composition entry-point for all Infrastructure sub-modules
+/// (Persistence, Scraping, Workers).
+/// </summary>
+/// <remarks>
+/// Call <see cref="AddMarathonInfrastructure"/> once from the host's DI
+/// setup. This replaces the previous reflection-based wiring in
+/// <c>App.xaml.cs::TryAddApplicationAndInfrastructure</c>.
+/// </remarks>
+public static class InfrastructureModule
+{
+    /// <summary>
+    /// Registers the complete Infrastructure layer:
+    /// <list type="bullet">
+    ///   <item>EF Core / SQLite persistence (<see cref="PersistenceModule.AddMarathonPersistence"/>).</item>
+    ///   <item>HttpClient + AngleSharp + Polly scraping (<see cref="ScrapingModule.AddMarathonScraping"/>).</item>
+    ///   <item><see cref="WorkerOptions"/> bound to the <c>Workers</c> config section.</item>
+    ///   <item>Three <see cref="Microsoft.Extensions.Hosting.BackgroundService"/> pollers.</item>
+    /// </list>
+    /// </summary>
+    public static IServiceCollection AddMarathonInfrastructure(
+        this IServiceCollection services,
+        IConfiguration config)
+    {
+        ArgumentNullException.ThrowIfNull(services);
+        ArgumentNullException.ThrowIfNull(config);
+
+        services.AddMarathonPersistence(config);
+        services.AddMarathonScraping(config);
+
+        services
+            .AddOptions<WorkerOptions>()
+            .Bind(config.GetSection(WorkerOptions.SectionName));
+
+        services.AddHostedService<UpcomingEventsPoller>();
+        services.AddHostedService<LiveOddsPoller>();
+        services.AddHostedService<ResultsWatchListPoller>();
+
+        return services;
+    }
+}