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).

CLAUDE.md

@@ -110,6 +110,28 @@ Marathon_<YYYY-MM-DD>_to_<YYYY-MM-DD>.xlsx
 - **`Directory.Build.props` must NOT set `TargetFramework`** when projects in the
   same solution use different TFMs (e.g., `net8.0` vs `net8.0-windows`).
 
+## Feature: Initial Implementation > Phase 4: Application + Workers — Learnings
+
+- **Two `WorkerOptions` classes coexist** with the same JSON shape but different namespaces:
+  `Marathon.Infrastructure.Configuration.WorkerOptions` (immutable `init`, used by workers)
+  and `Marathon.UI.Services.WorkerOptions` (mutable `set`, used by Settings page).
+  Both bind to `"Workers"` in `appsettings.json`. Keep them in sync when adding new keys.
+- **`Microsoft.Extensions.Logging.EventId` conflicts with `Marathon.Domain.ValueObjects.EventId`**
+  in any project that adds `Microsoft.Extensions.Logging.Abstractions`. Fix with a global alias
+  in `GlobalUsings.cs`: `global using LogEventId = Microsoft.Extensions.Logging.EventId;`
+  and local file aliases where both are used together.
+- **NSubstitute cannot proxy `sealed` classes.** Use cases are `sealed record` or `sealed class`.
+  Worker tests must build a real use-case instance backed by substituted interfaces rather than
+  substituting the use case directly.
+- **`BackgroundService` workers are singletons; use cases are scoped.** Always resolve scoped
+  use cases via `IServiceProvider.CreateAsyncScope()` inside the worker loop — never inject them
+  directly into the constructor.
+- **Cronos 6-field cron format.** Pass `CronFormat.IncludeSeconds` to `CronExpression.Parse`
+  when the expression has a seconds field (e.g., `"0 0 */6 * * *"`). Default Cronos parse
+  expects 5-field (no seconds).
+- **`ApplicationModule.AddMarathonApplication` takes no `IConfiguration`** — the Application
+  layer has no config bindings of its own. Infrastructure and UI bind their own options sections.
+
 ## Feature: Initial Implementation > Phase 0: Scraping Spike — Learnings
 
 (Permanent learnings about marathonbet.by data shape, anti-bot, page structure.