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/Anomalies/Insights.razor

@@ -15,6 +15,7 @@
 @inject IStringLocalizer<SharedResource> L
 @inject IAnomalyInsightsService InsightsService
 @inject NavigationManager Nav
+@inject ILogger<Insights> Logger
 
 <PageTitle>@L["App.Title"] · @L["Nav.Insights"]</PageTitle>
 
@@ -658,8 +659,9 @@
             _vm = report;
         }
         catch (OperationCanceledException) { /* superseded */ }
-        catch
+        catch (Exception ex)
         {
+            Logger.LogError(ex, "Insights: failed to build the anomaly outcome report.");
             _errored = true;
             _vm = null;
         }

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"],

src/Marathon.UI/Pages/Shared/EventListShell.razor

@@ -14,6 +14,7 @@
 @using DomainEventId = Marathon.Domain.ValueObjects.EventId
 @implements IDisposable
 @inject IStringLocalizer<SharedResource> L
+@inject ILogger<EventListShell> Logger
 
 <section class="m-shell">
     <header class="m-rise m-rise-1" style="display: grid; gap: var(--m-space-3); max-width: 880px;">
@@ -364,7 +365,11 @@
 
     private void StartTimer()
     {
-        _refreshTimer?.Dispose();
+        if (_refreshTimer is not null)
+        {
+            _refreshTimer.Elapsed -= OnRefreshTimerElapsed;
+            _refreshTimer.Dispose();
+        }
         var interval = Math.Max(5, AutoRefreshSeconds) * 1000.0;
         _refreshTimer = new System.Timers.Timer(interval) { AutoReset = true };
         _refreshTimer.Elapsed += OnRefreshTimerElapsed;
@@ -383,10 +388,11 @@
         {
             await InvokeAsync(LoadAsync);
         }
-        catch
+        catch (Exception ex)
         {
-            // Swallowed — LoadAsync already handles its own errors; this catch
-            // is the last line of defense for InvokeAsync itself.
+            // Last line of defense for InvokeAsync itself — LoadAsync handles its
+            // own errors. Log rather than silently dropping the failure.
+            Logger.LogError(ex, "EventListShell ({Surface}): auto-refresh tick failed.", Surface);
         }
     }
 
@@ -414,9 +420,10 @@
         {
             // Swallow — superseded by a newer load.
         }
-        catch
+        catch (Exception ex)
         {
-            // Hide errors from the UI; Phase 9 will add a snackbar.
+            // Degrade gracefully (clear the rows) but record the failure for diagnosis.
+            Logger.LogError(ex, "EventListShell ({Surface}): failed to load event rows.", Surface);
             _rows = new List<EventListItem>();
         }
         finally
@@ -523,7 +530,11 @@
 
     public void Dispose()
     {
-        _refreshTimer?.Dispose();
+        if (_refreshTimer is not null)
+        {
+            _refreshTimer.Elapsed -= OnRefreshTimerElapsed;
+            _refreshTimer.Dispose();
+        }
         _searchCts?.Cancel();
         _searchCts?.Dispose();
         _loadCts?.Cancel();