Fix DbUpdateException in TradeRepository and Polymarket API 400 on max offset

src/Predictalytics.Infrastructure/Data/Repositories/TradeRepository.cs

@@ -69,7 +69,20 @@ public class TradeRepository : ITradeRepository
             {
                 try { _db.Entry(t).State = EntityState.Detached; } catch { }
             }
-            throw;
+
+            // Fallback to inserting one by one to avoid losing the entire batch due to a single duplicate
+            foreach (var t in trades)
+            {
+                try
+                {
+                    _db.Trades.Add(t);
+                    await _db.SaveChangesAsync(ct);
+                }
+                catch
+                {
+                    try { _db.Entry(t).State = EntityState.Detached; } catch { }
+                }
+            }
         }
     }