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/Domain/Nomination.cs

@@ -5,13 +5,32 @@ public sealed class Nomination
     public int Id { get; set; }
     public int SeasonId { get; set; }
     public Season Season { get; set; } = null!;
-    public int CategoryId { get; set; }
-    public Category Category { get; set; } = null!;
+    public int? CategoryId { get; set; }
+    public Category? Category { get; set; }
+    public string CategoryGroupName { get; set; } = string.Empty;
     public string SubmittedByTwitchId { get; set; } = string.Empty;
     public int? CandidateId { get; set; }
     public Candidate? Candidate { get; set; }
+    public int? StreamerIdentityId { get; set; }
+    public StreamerIdentity? StreamerIdentity { get; set; }
+    public int? SuggestedCategoryId { get; set; }
+    public Category? SuggestedCategory { get; set; }
     public string? CandidateText { get; set; }
     public string? StreamUrl { get; set; }
+    public string? ResolvedChannel { get; set; }
+    public string? ResolvedPlatform { get; set; }
+    public int? AvgViewers { get; set; }
+    public int? HoursStreamed { get; set; }
+    public int? HoursWatched { get; set; }
+    public int? PeakViewers { get; set; }
+    public int? FollowersGained { get; set; }
+    public string TrackerStatus { get; set; } = "pending";
+    public DateTimeOffset? TrackerCheckedAt { get; set; }
+    public string TrackingReviewStatus { get; set; } = "clear";
+    public string TrackingFlagsJson { get; set; } = "[]";
+    public string? TrackingReviewNote { get; set; }
+    public string? TrackingReviewedByTwitchId { get; set; }
+    public DateTimeOffset? TrackingReviewedAt { get; set; }
     public string Status { get; set; } = "pending";
     public string? ReviewNote { get; set; }
     public string? ReviewedByTwitchId { get; set; }