Add winner archive, host image upload and live demo data

Deliver the demo-ready feature set and seed data so the live site can be
presented end to end:

- Winner archive: ArchivedWinner domain, admin CRUD endpoints/view/manager
  and public archive surface, backed by AddArchivedWinners migration.
- Host presentation: host image upload and artist name on SiteSettings with
  public image endpoint and supporting migrations.
- Clip submissions: idempotent table-ensure migration plus current-season
  demo clips for review workflows.
- Demo seed data: sponsors, share links and 2025 archived winners, with a
  guarded RemoveDemoSeasons cleanup; all seeds guard against real data.
- EnsureRuntimeSchemaParity migration to align runtime schema defensively.
- Admin/home UI refinements; remove unused team role permissions modal and
  dead share-quick-links code.

All seed and schema migrations are idempotent (IF NOT EXISTS / ON CONFLICT)
and skip when real season data is present.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

Backend/Endpoints/AdminSeasonDetailEndpoints.cs

@@ -23,11 +23,11 @@ public static partial class AdminSeasonManagementEndpoints
             .FirstOrDefaultAsync(item => item.Id == 1);
         var trackingRules = TrackingRulesSettings.Read(settings);
 
-        var candidates = await db.Candidates
+        var candidateRows = await db.Candidates
             .AsNoTracking()
             .Where(item => item.SeasonId == seasonId)
             .OrderBy(item => item.DisplayName)
-            .Select(item => new AdminCandidateItemDto(
+            .Select(item => new AdminCandidateRow(
                 item.Id,
                 item.CategoryId,
                 item.StreamerIdentityId,
@@ -43,7 +43,7 @@ public static partial class AdminSeasonManagementEndpoints
                 item.ClipEmbedStatus))
             .ToArrayAsync();
 
-        var candidateCounts = candidates
+        var candidateCounts = candidateRows
             .GroupBy(item => item.CategoryId)
             .ToDictionary(grouping => grouping.Key, grouping => grouping.Count());
 
@@ -217,6 +217,11 @@ public static partial class AdminSeasonManagementEndpoints
                 item.CategoryId,
                 item.CandidateId))
             .ToArrayAsync();
+        var candidates = BuildCandidateItems(
+            candidateRows,
+            pendingNominationRows,
+            reviewedNominationRows,
+            votingEntryRows);
         var votingWorkspace = BuildVotingWorkspace(
             categories,
             candidates,
@@ -281,6 +286,21 @@ public static partial class AdminSeasonManagementEndpoints
         int CategoryId,
         int CandidateId);
 
+    private sealed record AdminCandidateRow(
+        int Id,
+        int CategoryId,
+        int? StreamerIdentityId,
+        string DisplayName,
+        string ChannelSlug,
+        string Platform,
+        int NominationTally,
+        string AcceptanceStatus,
+        string? AcceptanceNote,
+        string? ClipCompilationUrl,
+        string? ClipCompilationTitle,
+        string? ClipCompilationPlatform,
+        string ClipEmbedStatus);
+
     private sealed record AdminNominationRow(
         int Id,
         int? CategoryId,
@@ -314,6 +334,79 @@ public static partial class AdminSeasonManagementEndpoints
         string? ReviewedByTwitchId,
         DateTimeOffset? ReviewedAt);
 
+    private static AdminCandidateItemDto[] BuildCandidateItems(
+        AdminCandidateRow[] candidateRows,
+        AdminNominationRow[] pendingNominationRows,
+        AdminNominationRow[] reviewedNominationRows,
+        AdminVotingEntryRow[] votingEntryRows)
+    {
+        var allNominationRows = pendingNominationRows
+            .Concat(reviewedNominationRows)
+            .ToArray();
+        var voteCountByCandidate = votingEntryRows
+            .GroupBy(item => item.CandidateId)
+            .ToDictionary(group => group.Key, group => group.Count());
+
+        return candidateRows
+            .Select(item => new AdminCandidateItemDto(
+                item.Id,
+                item.CategoryId,
+                item.StreamerIdentityId,
+                item.DisplayName,
+                item.ChannelSlug,
+                item.Platform,
+                ResolveCandidateAvgViewers(item, allNominationRows),
+                voteCountByCandidate.GetValueOrDefault(item.Id, 0),
+                item.NominationTally,
+                item.AcceptanceStatus,
+                item.AcceptanceNote,
+                item.ClipCompilationUrl,
+                item.ClipCompilationTitle,
+                item.ClipCompilationPlatform,
+                item.ClipEmbedStatus))
+            .ToArray();
+    }
+
+    private static int? ResolveCandidateAvgViewers(AdminCandidateRow candidate, AdminNominationRow[] nominationRows)
+    {
+        var directMatch = nominationRows
+            .Where(item => item.CandidateId == candidate.Id && item.AvgViewers.HasValue)
+            .OrderByDescending(item => item.TrackerCheckedAt ?? item.ReviewedAt ?? item.CreatedAt)
+            .Select(item => item.AvgViewers)
+            .FirstOrDefault();
+        if (directMatch.HasValue)
+        {
+            return directMatch.Value;
+        }
+
+        if (candidate.StreamerIdentityId.HasValue)
+        {
+            var identityMatch = nominationRows
+                .Where(item => item.StreamerIdentityId == candidate.StreamerIdentityId && item.AvgViewers.HasValue)
+                .OrderByDescending(item => item.TrackerCheckedAt ?? item.ReviewedAt ?? item.CreatedAt)
+                .Select(item => item.AvgViewers)
+                .FirstOrDefault();
+            if (identityMatch.HasValue)
+            {
+                return identityMatch.Value;
+            }
+        }
+
+        var normalizedChannel = candidate.ChannelSlug.Trim().TrimStart('@').ToLowerInvariant();
+        if (string.IsNullOrWhiteSpace(normalizedChannel))
+        {
+            return null;
+        }
+
+        return nominationRows
+            .Where(item =>
+                item.AvgViewers.HasValue
+                && string.Equals(item.ResolvedChannel?.Trim().TrimStart('@'), normalizedChannel, StringComparison.OrdinalIgnoreCase))
+            .OrderByDescending(item => item.TrackerCheckedAt ?? item.ReviewedAt ?? item.CreatedAt)
+            .Select(item => item.AvgViewers)
+            .FirstOrDefault();
+    }
+
     private static AdminNominationReviewItemDto ToNominationReviewItem(
         AdminNominationRow item,
         IEnumerable<dynamic> categoryRows,