Fix Aggregated-tier mutable-bucket vs checkpoint bug

The Aggregated ingest tier bucketed trades by hour incl. the current, still-growing
hour, then upserted via ON DUPLICATE KEY UPDATE (mutable rows). The PnL engine
checkpoints positions by row Id, so a bucket that keeps growing after being applied
had its later growth silently skipped (Id <= LastAppliedTradeId).

Extract the duplicated aggregation logic from PollingWorker + TradeHistoryWorker into
TradeAggregation.AggregateCompletedHours, which only aggregates COMPLETED hours; the
current hour is deferred (re-fetched next cycle) so every persisted aggregate is
immutable. +3 unit tests.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

src/Predictalytics.Application.Tests/Services/TradeAggregationTests.cs

@@ -0,0 +1,81 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using Predictalytics.Application.Services;
+using Predictalytics.Domain.Entities;
+using Predictalytics.Domain.Enums;
+using Xunit;
+
+namespace Predictalytics.Application.Tests.Services;
+
+public class TradeAggregationTests
+{
+    private static Trade Raw(int outcomeId, TradeSide side, decimal price, decimal size, DateTime at)
+        => new()
+        {
+            MarketOutcomeId = outcomeId, DbMarketId = 10, MarketId = "cond", AssetId = "asset",
+            Outcome = "Yes", Side = side, Price = price, Size = size, Amount = price * size, ExecutedAt = at
+        };
+
+    [Fact]
+    public void AggregateCompletedHours_SumsCompletedHourWithVwap()
+    {
+        var now = new DateTime(2026, 07, 13, 15, 30, 0, DateTimeKind.Utc);
+        var completedHour = new DateTime(2026, 07, 13, 10, 0, 0, DateTimeKind.Utc);
+
+        var trades = new List<Trade>
+        {
+            Raw(100, TradeSide.Buy, 0.40m, 50m, completedHour.AddMinutes(5)),
+            Raw(100, TradeSide.Buy, 0.60m, 50m, completedHour.AddMinutes(45)),
+        };
+
+        var result = TradeAggregation.AggregateCompletedHours(trades, traderId: 7, nowUtc: now);
+
+        var agg = Assert.Single(result);
+        Assert.Equal("AGG_7_100_Buy_2026071310", agg.PlatformTradeId);
+        Assert.Equal(100m, agg.Size);            // 50 + 50
+        Assert.Equal(50m, agg.Amount);           // 0.40*50 + 0.60*50 = 20 + 30
+        Assert.Equal(0.50m, agg.Price);          // VWAP = 50/100
+        Assert.Equal(2, agg.AggregatedCount);
+    }
+
+    [Fact]
+    public void AggregateCompletedHours_DefersCurrentHour()
+    {
+        // The bug this guards against: the current, still-growing hour must NOT be aggregated,
+        // because its aggregate row is mutable-by-key while the PnL engine checkpoints by Id.
+        var now = new DateTime(2026, 07, 13, 15, 30, 0, DateTimeKind.Utc);
+
+        var trades = new List<Trade>
+        {
+            // completed hour -> aggregated
+            Raw(100, TradeSide.Buy, 0.50m, 40m, new DateTime(2026, 07, 13, 14, 10, 0, DateTimeKind.Utc)),
+            // current hour (15:xx) -> deferred
+            Raw(100, TradeSide.Buy, 0.50m, 99m, new DateTime(2026, 07, 13, 15, 05, 0, DateTimeKind.Utc)),
+        };
+
+        var result = TradeAggregation.AggregateCompletedHours(trades, traderId: 7, nowUtc: now);
+
+        Assert.Single(result);                                   // only the 14:00 bucket
+        Assert.EndsWith("_2026071314", result[0].PlatformTradeId);
+        Assert.Equal(40m, result[0].Size);                       // current-hour 99 shares NOT included
+    }
+
+    [Fact]
+    public void AggregateCompletedHours_SeparatesOutcomeAndSide()
+    {
+        var now = new DateTime(2026, 07, 13, 15, 0, 0, DateTimeKind.Utc);
+        var h = new DateTime(2026, 07, 13, 12, 0, 0, DateTimeKind.Utc);
+
+        var trades = new List<Trade>
+        {
+            Raw(100, TradeSide.Buy,  0.50m, 10m, h),
+            Raw(100, TradeSide.Sell, 0.50m, 10m, h),
+            Raw(101, TradeSide.Buy,  0.50m, 10m, h),
+        };
+
+        var result = TradeAggregation.AggregateCompletedHours(trades, traderId: 7, nowUtc: now);
+
+        Assert.Equal(3, result.Count); // (100,Buy), (100,Sell), (101,Buy) are distinct buckets
+    }
+}