Add viewer-range categories, nomination tracking, dynamic showact form, session timeout, share URLs, and workflow-per-season

Features:
- Category viewer ranges + subcategory templates (admin group modal, tree workspace)
- Nomination enrichment via TwitchTracker API (NominationEnrichmentService,
  TwitchTrackerViewerStatsProvider) with admin tracking rules editor
- Nomination group tracker: CategoryGroupName as primary identifier,
  CategoryId stays as nullable legacy field; StreamerIdentity table
- Dynamic showact application form builder (AdminShowactFormBuilder,
  ShowactApplicationSchedule)
- Session idle timeout setting (AdminSessionTimeoutCard)
- Share URLs for X and Discord (SiteSettings, public extras)
- Workflow rules now stored per season (falls back to global SiteSettings)
- New admin routes: settings/access, settings/workflows, tracking-rules
- New admin review workspace with subcategory tabs
- AdminCategoriesView rebuilt with group/subcategory modals

Migrations (all additive):
- AddShareUrls, AddShowactDynamicForm, AddCategoryViewerRanges,
  AddSessionIdleTimeoutSettings, AddSeasonSubcategoryTemplates,
  AddNominationGroupTrackerIdentity, AddShowactApplicationSchedule,
  AddSeasonWorkflowRulesJson

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Backend/Endpoints/PublicUserParticipationEndpoints.cs

@@ -36,6 +36,7 @@ public static partial class PublicEndpoints
             .Select(item => new
             {
                 item.CategoryId,
+                item.CategoryGroupName,
                 item.Status,
                 Nominee = item.CandidateId != null
                     ? item.Candidate!.DisplayName
@@ -46,9 +47,10 @@ public static partial class PublicEndpoints
         var groupedNominations = nominations
             .Where(item => item.Status != "rejected" && item.Status != "superseded")
             .Where(item => !string.IsNullOrWhiteSpace(item.Nominee))
-            .GroupBy(item => item.CategoryId)
+            .GroupBy(item => new { item.CategoryId, item.CategoryGroupName })
             .Select(group => new UserNominationStateDto(
-                group.Key,
+                group.Key.CategoryId,
+                group.Key.CategoryGroupName,
                 group.Select(item => item.Nominee!)
                     .Distinct(StringComparer.OrdinalIgnoreCase)
                     .ToArray()))