fix: Remove compiler warnings in Application & Web

- KisApiPriceSource.cs: Use discard pattern for unused exception variables
- Monitoring/Index.cshtml: Handle nullable TotalErrors with null coalescing

Build now passes with 0 code-level warnings (6 remaining NuGet compatibility warnings are harmless).

Co-Authored-By: Claude Haiku 4.5 <noreply@anthropic.com>

src/dotnet/QuantEngine.Application/Services/KisApiPriceSource.cs

@@ -51,7 +51,7 @@ public class KisApiPriceSource : IPriceSource
                 result.OrderbookStatus = "OK";
                 result.OrderbookRaw = output1;
             }
-            catch (Exception ex)
+            catch (Exception)
             {
                 result.OrderbookStatus = "ERROR";
             }
@@ -70,7 +70,7 @@ public class KisApiPriceSource : IPriceSource
                 result.ShortSaleStatus = "OK";
                 result.ShortSaleRaw = (Dictionary<string, object>?)rows.FirstOrDefault() ?? new();
             }
-            catch (Exception ex)
+            catch (Exception)
             {
                 result.ShortSaleStatus = "ERROR";
             }