feat(my-bets): personal bet journal with CLV tracking

Adds a manual bet-tracking journal that turns the analyzer into an actual
bet tracker. Users record wagers; the journal auto-grades them when event
results land and computes per-bet Closing-Line-Value against the latest
pre-match snapshot — the strongest long-run indicator of betting skill.

Domain:
- PlacedBet entity (reuses Bet vocabulary for Scope/Type/Side/Value/Rate)
  with stake, placed-at, outcome, and notes. Derived GrossReturn / NetProfit.
- BetOutcome enum (Pending / Won / Lost / Void).
- BetOutcomeResolver: pure function grading any Match-scope bet against an
  EventResult. Handles 1X2, draws, handicap (incl. push), and totals.
  Period-scope bets stay manual since EventResult only carries full-time.

Application:
- IPlacedBetRepository abstraction.
- ClosingLineValueCalculator: pure CLV math (implied-probability delta) +
  snapshot-matching predicate by Scope/Type/Side/Value.
- BetJournalReport + BetJournalStats records.
- Four use cases: Record / ResolvePending / BuildReport / Delete.
- New ISnapshotRepository.GetLatestPreMatchAsync pushes the closing-line
  pick into a single SQLite query rather than materialising the 30-day
  window in memory per event.
- ROI turnover excludes Void stakes — pushes are not real turnover and
  including them would dilute the user's edge.

Infrastructure:
- PlacedBetEntity / Configuration / Repository / Mapping helpers.
- 20260516 migration adding the PlacedBets table with EventCode and
  Outcome indices. Intentionally NO foreign key to Events — the journal
  is user data and must survive snapshot-retention pruning. Covered by an
  explicit round-trip test.

UI:
- Pages/MyBets/Journal.razor: hero header, 4-card KPI strip (ROI / strike
  rate / avg CLV / net profit, tinted by tone), inline add-bet form with
  the same invariants as the Bet record, drill-down table with per-row
  outcome pills, CLV percentage-points column, P&L, notes underline, and
  inline-confirm delete. RU + EN i18n.
- Nav entry under Analysis.

Tests: +55 across Domain / Application / Infrastructure (resolver math
including handicap push and total push boundaries, PlacedBet invariants
and derived properties, CLV math + null-handling, four use cases under
NSubstitute, EF round-trip including survives-event-deletion). All 379
tests pass.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

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

@@ -83,4 +83,26 @@ internal sealed class SnapshotRepository : ISnapshotRepository
 
     public async Task SaveChangesAsync(CancellationToken ct = default) =>
         await _db.SaveChangesAsync(ct);
+
+    public async Task<OddsSnapshot?> GetLatestPreMatchAsync(
+        EventId eventId,
+        DateTimeOffset atOrBefore,
+        CancellationToken ct = default)
+    {
+        // OddsSource enum: PreMatch == 0. Inlined as an int constant to keep the
+        // expression EF-translatable (the IL would otherwise carry a cast).
+        const int preMatchSource = (int)Marathon.Domain.Enums.OddsSource.PreMatch;
+
+        var toStr = atOrBefore.ToString("O");
+
+        var entity = await _db.Snapshots.AsNoTracking()
+            .Include(s => s.Bets)
+            .Where(s => s.EventCode == eventId.Value
+                     && s.Source == preMatchSource
+                     && s.CapturedAt.CompareTo(toStr) <= 0)
+            .OrderByDescending(s => s.CapturedAt)
+            .FirstOrDefaultAsync(ct);
+
+        return entity is null ? null : Mapping.ToDomain(entity);
+    }
 }