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.Application/Betting/ClosingLineValueCalculator.cs

@@ -0,0 +1,85 @@
+using Marathon.Domain.Entities;
+using Marathon.Domain.ValueObjects;
+
+namespace Marathon.Application.Betting;
+
+/// <summary>
+/// Pure helper that computes Closing Line Value (CLV) for a placed bet.
+/// </summary>
+/// <remarks>
+/// <para>
+/// CLV measures how much better (or worse) the rate the user took was compared
+/// with the bookmaker's last pre-match price on the same selection. It is the
+/// single best long-run indicator of betting skill — positive CLV correlates
+/// with positive expected value regardless of any individual bet's outcome.
+/// </para>
+/// <para>
+/// Formula (implied-probability delta):
+/// <list type="bullet">
+///   <item>Taken implied probability:   <c>p_t = 1 / takenRate</c></item>
+///   <item>Closing implied probability: <c>p_c = 1 / closeRate</c></item>
+///   <item><c>CLV  =  p_c − p_t</c></item>
+/// </list>
+/// Positive CLV means the closing price implied higher probability for the
+/// selection than the price the user took — i.e. the line moved in the user's
+/// favour after they placed the bet.
+/// </para>
+/// <para>
+/// Returns <c>null</c> when no matching bet (same Scope / Type / Side / Value)
+/// can be found in the closing snapshot — typically because the market closed
+/// before the bookmaker exposed a comparable line, or the snapshot store has
+/// gaps. UI consumers must distinguish "no data" from "0% CLV".
+/// </para>
+/// </remarks>
+public static class ClosingLineValueCalculator
+{
+    /// <summary>
+    /// Computes CLV (implied-probability delta) given the rate the user took
+    /// and the rate present in the closing pre-match snapshot for the same
+    /// selection. Both must be positive — invariants on <see cref="OddsRate"/>
+    /// already guarantee this for inputs sourced from the domain.
+    /// </summary>
+    public static decimal Compute(decimal takenRate, decimal closingRate)
+    {
+        if (takenRate <= 0m)
+            throw new ArgumentOutOfRangeException(nameof(takenRate), takenRate, "Must be positive.");
+        if (closingRate <= 0m)
+            throw new ArgumentOutOfRangeException(nameof(closingRate), closingRate, "Must be positive.");
+
+        var takenProb = 1m / takenRate;
+        var closingProb = 1m / closingRate;
+
+        // Round to 6 decimals — beyond that is noise from the round-trip.
+        return Math.Round(closingProb - takenProb, 6);
+    }
+
+    /// <summary>
+    /// Convenience overload: finds the matching <see cref="Bet"/> in
+    /// <paramref name="closingSnapshot"/> by Scope / Type / Side / Value, then
+    /// computes CLV against <paramref name="takenRate"/>. Returns <c>null</c>
+    /// when no comparable bet is present.
+    /// </summary>
+    public static decimal? TryCompute(
+        decimal takenRate,
+        Bet placedSelection,
+        OddsSnapshot? closingSnapshot)
+    {
+        ArgumentNullException.ThrowIfNull(placedSelection);
+        if (closingSnapshot is null) return null;
+
+        var match = closingSnapshot.Bets.FirstOrDefault(b =>
+            b.Scope.Equals(placedSelection.Scope) &&
+            b.Type == placedSelection.Type &&
+            b.Side == placedSelection.Side &&
+            NullableValuesEqual(b.Value, placedSelection.Value));
+
+        return match is null ? null : Compute(takenRate, match.Rate.Value);
+    }
+
+    private static bool NullableValuesEqual(OddsValue? a, OddsValue? b)
+    {
+        if (a is null && b is null) return true;
+        if (a is null || b is null) return false;
+        return a.Value == b.Value;
+    }
+}