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

src/Predictalytics.Infrastructure/Providers/Polymarket/PolymarketApiClient.cs

@@ -111,6 +111,16 @@ public class PolymarketApiClient
         return result ?? [];
     }
 
+    /// <summary>
+    /// Fetch CLOB orderbook for a given token ID.
+    /// </summary>
+    public async Task<OrderBookResponse?> GetOrderBookAsync(string tokenId, CancellationToken ct = default)
+    {
+        var url = $"/book?token_id={tokenId}";
+        _logger.LogDebug("Fetching orderbook for token: {TokenId}", tokenId);
+        return await ExecuteWithRetryAsync<OrderBookResponse>(_clobClient, url, "CLOB", ct);
+    }
+
     private async Task<T?> ExecuteWithRetryAsync<T>(HttpClient client, string url, string endpointGroup, CancellationToken ct, int attempt = 1)
     {
         await _rateLimiter.WaitAsync(PlatformType.Polymarket, ct, endpointGroup);

src/Predictalytics.Infrastructure/Providers/Polymarket/PolymarketModels.cs

@@ -138,6 +138,9 @@ public class GammaMarketResponse
     [JsonPropertyName("active")] public bool Active { get; set; }
     [JsonPropertyName("resolved")] public bool Resolved { get; set; }
     [JsonPropertyName("resolution_outcome")] public string? ResolutionOutcome { get; set; }
+    [JsonPropertyName("negRisk")] public bool NegRisk { get; set; }
+    [JsonPropertyName("closedTime")] public string? ClosedTime { get; set; }
+    [JsonPropertyName("takerFee")] [JsonConverter(typeof(FlexibleDoubleConverter))] public double TakerFee { get; set; }
 
     /// <summary>JSON string of outcomes, e.g. "[\"Yes\", \"No\"]"</summary>
     [JsonPropertyName("outcomes")] public string? Outcomes { get; set; }
@@ -165,6 +168,18 @@ public class GammaEventResponse
     [JsonPropertyName("markets")] public List<GammaMarketResponse> Markets { get; set; } = [];
 }
 
+public class OrderBookResponse
+{
+    [JsonPropertyName("bids")] public List<OrderBookLevel> Bids { get; set; } = [];
+    [JsonPropertyName("asks")] public List<OrderBookLevel> Asks { get; set; } = [];
+}
+
+public class OrderBookLevel
+{
+    [JsonPropertyName("price")] public string Price { get; set; } = "0";
+    [JsonPropertyName("size")] public string Size { get; set; } = "0";
+}
+
 public class GammaTagResponse
 {
     [JsonPropertyName("id")] public string Id { get; set; } = "";

src/Predictalytics.Infrastructure/Providers/Polymarket/PolymarketProvider.cs

@@ -302,7 +302,10 @@ public class PolymarketProvider : IPlatformProvider
             DbCreatedAt = DateTime.UtcNow,
             IsResolved = raw.Resolved || raw.Closed,
             ResolutionOutcome = raw.ResolutionOutcome,
-            LastUpdatedAt = DateTime.UtcNow
+            LastUpdatedAt = DateTime.UtcNow,
+            FeeRateBps = (decimal)(raw.TakerFee * 10000),
+            IsNegRisk = raw.NegRisk,
+            ClosedAt = DateTime.TryParse(raw.ClosedTime, out var mct) ? mct : null
         };
 
         // Parse outcomes, prices, and token IDs from JSON strings