fix(initial-implementation): close P2/P3/P5 review blockers — 185/185 tests green

Combined-batch reviewer flagged three real blockers + two test-infra
issues across the parallel P2/P3/P5 batch. All resolved:

PHASE 3 — DateTimeOffset UTC-kind constructor (3 sites)
  EventListingParserBase.cs:39, EventOddsParser.cs:72, ResultsParser.cs:104
  Replaced `new DateTimeOffset(DateTimeOffset.UtcNow.UtcDateTime, MoscowOffset)`
  (throws ArgumentException because UtcDateTime has Kind=Utc) with
  `DateTimeOffset.UtcNow.ToOffset(MoscowOffset)`.

PHASE 2 — EF string.Compare not translatable (3 sites)
  EventRepository.cs:34, SnapshotRepository.cs:46, ExcelExporter.cs:35
  Replaced `string.Compare(col, str, StringComparison.Ordinal)` with
  `col.CompareTo(str)` so EF Core's SQLite provider can translate the
  expression. Semantics unchanged (SQLite default collation = BINARY = ordinal).

PHASE 3 — ServerTimeProvider regex misses JSON-quoted key
  Regex `serverTime\s*:\s*"..."` only matched bare-key form. Updated to
  `"?serverTime"?\s*:\s*"..."` so the JSON-quoted form (the actual
  marathonbet.by production format) is matched.

PHASE 3 — fixture: orphan <td> elements stripped by HTML5 parser
  tests/.../Fixtures/marathonbet/event-football-sample.html — wrapped
  the <td> blocks in a proper <table><tbody><tr> hierarchy so AngleSharp
  preserves them and `td.Closest("td")` succeeds in the parser.

PHASE 2 — InMemoryDbFixture shared state across parallel tests
  All fixture instances used `Data Source=marathon_tests` causing xUnit's
  parallel-within-class runs to contaminate each other's data. Each fixture
  now uses a Guid-suffixed unique data source name.

PLAN.md — P2/P3/P5 rows updated to ✅ Done with batch commit reference.

Test status:
  Domain.Tests:         96/96 ✅
  Application.Tests:     1/1  ✅
  Infrastructure.Tests: 77/77 ✅
  UI.Tests:             11/11 ✅
  TOTAL:               185/185 ✅
Build: 0 warnings, 0 errors.

Deferred to later phases (per reviewer 🟡 / 🔵 notes):
- SnapshotRepository.GetAsync(Guid) uses lossy GetHashCode workaround;
  Phase 4 to fix or remove from interface.
- Excel Sport name column writes string.Empty (need lookup join in Phase 6).
- PeriodScopeMapper football n>2 falls through to "Quarter" token;
  guarded by MaxPeriods today, but defensive cleanup at Phase 9.
- Settings.razor duplicate m-rise-5 class on Localization section.

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

@@ -43,8 +43,8 @@ internal sealed class SnapshotRepository : ISnapshotRepository
         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)
+                     && s.CapturedAt.CompareTo(fromStr) >= 0
+                     && s.CapturedAt.CompareTo(toStr) <= 0)
             .ToListAsync(ct);
 
         return entities.Select(Mapping.ToDomain).ToList().AsReadOnly();