feat(replay): add ReplayHistoryReader for newest-first list query

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

SVSim.Database/Services/Replay/ReplayHistoryReader.cs

@@ -0,0 +1,27 @@
+using Microsoft.EntityFrameworkCore;
+
+namespace SVSim.Database.Services.Replay;
+
+public sealed class ReplayHistoryReader : IReplayHistoryReader
+{
+    private readonly SVSimDbContext _db;
+
+    public ReplayHistoryReader(SVSimDbContext db) => _db = db;
+
+    public async Task<IReadOnlyList<ReplayHistoryEntry>> GetRecentAsync(long viewerId, int take, CancellationToken ct)
+    {
+        return await _db.ViewerBattleHistories
+            .AsNoTracking()
+            .Where(h => h.ViewerId == viewerId)
+            .OrderByDescending(h => h.CreateTime)
+            .Take(take)
+            .Select(h => new ReplayHistoryEntry(
+                h.BattleId, h.BattleType, h.DeckFormat, h.TwoPickType, h.IsLimitTurn,
+                h.SelfClassId, h.SelfSubClassId, h.SelfCharaId, h.SelfRotationId,
+                h.OpponentClassId, h.OpponentSubClassId, h.OpponentCharaId,
+                h.OpponentName, h.OpponentCountryCode,
+                h.OpponentEmblemId, h.OpponentDegreeId, h.OpponentRotationId,
+                h.IsWin, h.BattleStartTime, h.CreateTime))
+            .ToListAsync(ct);
+    }
+}