refactor(guild_chat): extract chat-user lookup to viewer repo; fix NEW-direction exclusivity

Add ChatUserProfile record and IViewerRepository.LoadChatProfilesAsync (AsNoTracking,
projects Name/EmblemId/CountryCode/Rank/DegreeId from Viewer+Info nav refs).
GuildChatController.Messages now injects IViewerRepository instead of SVSimDbContext;
calls LoadChatProfilesAsync to populate users[] (removes direct db access from controller).
GuildChatMessageRepository direction=2 (NEW): change >= start to > start (exclusive).
GuildChatPollTests updated to assert the start message is NOT returned by direction=NEW.

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

SVSim.Database/Repositories/Viewer/ViewerRepository.cs

@@ -296,6 +296,33 @@ public class ViewerRepository : IViewerRepository
             .ToDictionaryAsync(v => v.Id, v => v.DisplayName, ct);
     }
 
+    public async Task<IReadOnlyDictionary<long, ChatUserProfile>> LoadChatProfilesAsync(IReadOnlyCollection<long> viewerIds, CancellationToken ct = default)
+    {
+        if (viewerIds.Count == 0) return new Dictionary<long, ChatUserProfile>();
+        var rows = await _dbContext.Set<Models.Viewer>()
+            .AsNoTracking()
+            .Include(v => v.Info.SelectedEmblem)
+            .Include(v => v.Info.SelectedDegree)
+            .Where(v => viewerIds.Contains(v.Id))
+            .Select(v => new
+            {
+                v.Id,
+                v.DisplayName,
+                EmblemId    = v.Info.SelectedEmblem != null ? v.Info.SelectedEmblem.Id : 100_000_000L,
+                CountryCode = v.Info.CountryCode ?? "",
+                DegreeId    = v.Info.SelectedDegree != null ? (int)v.Info.SelectedDegree.Id : 0,
+            })
+            .ToListAsync(ct);
+        return rows.ToDictionary(
+            r => r.Id,
+            r => new ChatUserProfile(
+                Name:        r.DisplayName,
+                EmblemId:    r.EmblemId,
+                CountryCode: r.CountryCode,
+                Rank:        1, // TODO: real rank when rank tracking lands
+                DegreeId:    r.DegreeId));
+    }
+
     private async Task<Models.Viewer> BuildDefaultViewer(string displayName, int initialTutorialState = 1)
     {
         Models.Viewer viewer = new Models.Viewer