Fix API offset limit 400 Bad Request, implement requested UI/UX improvements

src/Predictalytics.Worker/Services/TradeRetentionWorker.cs

@@ -72,9 +72,10 @@ public class TradeRetentionWorker : BackgroundService
         var compactionCutoff = utcNow.Date.AddDays(-compactionDays);
 
         // 1. Prune Old Trades (C1 & C2)
+        // Exclude trades if the trader is on any active Watchlist
         _logger.LogInformation("Pruning trades older than {Cutoff}...", retentionCutoff);
         var deletedCount = await db.Trades
-            .Where(t => t.ExecutedAt < retentionCutoff)
+            .Where(t => t.ExecutedAt < retentionCutoff && !t.Trader.WatchlistEntries.Any())
             .ExecuteDeleteAsync(ct);
 
         _logger.LogInformation("Pruned {Count} old trades from the database.", deletedCount);