refactor: log silenced UI errors, fix timer leak, narrow exception catch

- EventListShell: detach the Elapsed handler before disposing the refresh timer
  (both StartTimer and Dispose) to stop a leaked subscription firing on a
  torn-down component; log the two previously-silent catches.
- Insights: log the previously-silent report-load catch.
- EventOddsParser: narrow catch(Exception) to catch(ArgumentException) so only
  the OddsRate/OddsValue/Bet guard-clause throws are swallowed.
- AnomalyEvidenceData: make the JSON DTOs init-only per the immutability convention.
- Settings: remove a dead DialogParameters block.

src/Marathon.UI/Pages/Settings.razor

@@ -282,13 +282,6 @@
 
     private async Task<bool> ConfirmAsync()
     {
-        var parameters = new DialogParameters
-        {
-            ["ContentText"] = L["Settings.Confirm.Body"].Value,
-            ["ButtonText"] = L["Settings.Action.Save"].Value,
-            ["CancelText"] = L["Common.Cancel"].Value,
-        };
-
         var result = await Dialogs.ShowMessageBox(
             title: L["Settings.Confirm.Title"],
             message: L["Settings.Confirm.Body"],