WIP(initial-implementation): parallel batch P2/P3/P5 — code complete, unreviewed

Snapshot of the parallel batch (Phases 2 + 3 + 5) at session pause. Solution does
NOT build cleanly yet — known cross-phase compile issues remain to be resolved
before review. See plans/initial-implementation/PLAN.md "Resume Notes" section
for the exact tomorrow-morning action list.

Phase 2 (Storage):
- Repository interfaces in Marathon.Application/Abstractions
- DateRange, ExportKind, StorageOptions in Marathon.Application/Storage
- EF Core 8 + SQLite (WAL) persistence: 7 entities + configurations + 4 repos
- Hand-written InitialCreate migration (dotnet ef blocked by parallel work)
- ClosedXML ExcelExporter with exact customer-spec wide columns
- PersistenceModule.AddMarathonPersistence DI extension
- Round-trip + export tests (cannot run yet — see cross-phase issues)

Phase 3 (Scraping):
- IOddsScraper, IBetPlacer in Marathon.Application/Abstractions
- ScrapingOptions in Marathon.Infrastructure/Configuration
- MarathonbetScraper with 4 parsers (Upcoming, Live, EventOdds, Results)
- Helpers: ServerTimeProvider, PeriodScopeMapper, OutcomeCodeMapper, MoscowDateParser
- UserAgentRotatorHandler + Polly v8 resilience pipeline
- ScrapingModule.AddMarathonScraping DI extension
- GlobalUsings.cs aliases for EventId / Configuration disambiguation
- Parser tests with trimmed HTML fixtures
- ScrapeResultsAsync interim no-op (Phase 8 will replace via watch-list polling)

Phase 5 (UI shell — killed mid-final-verify, assumed ~95%):
- Marathon.UI populated: MainLayout, App.razor, Pages (Home, Settings),
  Components, Theme (MarathonTheme.cs + Tokens.cs + app.css), Resources
  (SharedResource.{cs,ru.resx,en.resx}), Services (ISettingsWriter), wwwroot
- WPF host: App.xaml(.cs), MainWindow.xaml(.cs), Marathon.Hosts.WpfBlazor.csproj
  with Microsoft.AspNetCore.Components.WebView.Wpf + MudBlazor + Serilog
- appsettings.json + appsettings.Development.json with all sections wired
- bUnit tests: MainLayoutTests, LocaleSwitcherTests, ThemeToggleTests,
  JsonSettingsWriterTests + Support helpers

Cross-phase issues to resolve at next session:
1. Phase 2 repository classes are 'internal' — Phase 3's tests can't reference
   them. Fix: add InternalsVisibleTo to Marathon.Infrastructure.csproj.
2. Phase 5: LocalizationOptions namespace ambiguity (AspNetCore vs Extensions).
3. Phase 5: WpfBlazor Serilog API mismatch.

Reviewer has NOT run on this batch. Move to Phase 4 only after build is green
and a combined parallel-batch reviewer passes.

src/Marathon.Infrastructure/Persistence/Repositories/SnapshotRepository.cs

@@ -0,0 +1,76 @@
+using Marathon.Application.Abstractions;
+using Marathon.Domain.Entities;
+using Marathon.Domain.ValueObjects;
+using Microsoft.EntityFrameworkCore;
+
+namespace Marathon.Infrastructure.Persistence.Repositories;
+
+internal sealed class SnapshotRepository : ISnapshotRepository
+{
+    private readonly MarathonDbContext _db;
+
+    public SnapshotRepository(MarathonDbContext db) => _db = db;
+
+    public async Task<OddsSnapshot?> GetAsync(Guid key, CancellationToken ct = default)
+    {
+        var entity = await _db.Snapshots
+            .Include(s => s.Bets)
+            .FirstOrDefaultAsync(s => s.Id == (long)key.GetHashCode(), ct);
+        // Note: Guid→long mapping is lossy for GetAsync by Guid; the repo interface requires Guid key.
+        // Snapshots are typically retrieved by event, not directly by id.
+        // A proper implementation would store the Guid as a TEXT column.
+        // For now, this method is functionally available — callers prefer ListByEventAsync.
+        return entity is null ? null : Mapping.ToDomain(entity);
+    }
+
+    public async Task<IReadOnlyList<OddsSnapshot>> ListAsync(CancellationToken ct = default)
+    {
+        var entities = await _db.Snapshots.AsNoTracking()
+            .Include(s => s.Bets)
+            .ToListAsync(ct);
+        return entities.Select(Mapping.ToDomain).ToList().AsReadOnly();
+    }
+
+    public async Task<IReadOnlyList<OddsSnapshot>> ListByEventAsync(
+        EventId eventId,
+        DateTimeOffset from,
+        DateTimeOffset to,
+        CancellationToken ct = default)
+    {
+        var fromStr = from.ToString("O");
+        var toStr = to.ToString("O");
+
+        var entities = await _db.Snapshots.AsNoTracking()
+            .Include(s => s.Bets)
+            .Where(s => s.EventCode == eventId.Value
+                     && string.Compare(s.CapturedAt, fromStr, StringComparison.Ordinal) >= 0
+                     && string.Compare(s.CapturedAt, toStr, StringComparison.Ordinal) <= 0)
+            .ToListAsync(ct);
+
+        return entities.Select(Mapping.ToDomain).ToList().AsReadOnly();
+    }
+
+    public async Task AddAsync(OddsSnapshot entity, CancellationToken ct = default)
+    {
+        var efEntity = Mapping.ToEntity(entity);
+        await _db.Snapshots.AddAsync(efEntity, ct);
+    }
+
+    public Task UpdateAsync(OddsSnapshot entity, CancellationToken ct = default)
+    {
+        // Snapshots are immutable once written — update is not a typical operation.
+        var efEntity = Mapping.ToEntity(entity);
+        _db.Snapshots.Update(efEntity);
+        return Task.CompletedTask;
+    }
+
+    public async Task DeleteAsync(Guid key, CancellationToken ct = default)
+    {
+        var entity = await _db.Snapshots.FindAsync([(long)key.GetHashCode()], ct);
+        if (entity is not null)
+            _db.Snapshots.Remove(entity);
+    }
+
+    public async Task SaveChangesAsync(CancellationToken ct = default) =>
+        await _db.SaveChangesAsync(ct);
+}