fix: resolve nullable dereference warnings in list/detail pages

MilkStream.Client/Components/JobTree.razor

@@ -151,7 +151,7 @@
                 job.Status is EJobStatus.Queued or EJobStatus.Running or EJobStatus.Waiting
             );
             if (shouldFetch) {
-                var (children, since) = await FetchChildren(job.Id, null);
+                var (children, since) = await FetchChildren!(job.Id, null);
                 _childrenCache[job.Id] = children;
                 _sinceTimestamps[job.Id] = since ?? DateTime.UtcNow;
             }
@@ -200,7 +200,7 @@
 
             // Level 0: poll children for all active roots (segment progress update)
             if (Level == 0 && FetchChildren is not null) {
-                foreach (var root in Roots) {
+                foreach (var root in Roots!) {
                     if (root.Status is EJobStatus.Queued or EJobStatus.Running or EJobStatus.Waiting) {
                         hasActive = true;
                         visited.Add(root.Id);

MilkStream.Client/Components/Pages/AlbumDetail.razor

@@ -36,7 +36,7 @@
                     }
                 </div>
                 <div class="d-flex align-items-center gap-2 mt-1">
-                    @if (!string.IsNullOrEmpty(album.PersonName) && album.Person.HasValue) {
+                    @if (!string.IsNullOrEmpty(album!.PersonName) && album.Person.HasValue) {
                         <a class="album-cosplayer-link" href="/cosplayer/@album.Person.Value">@album.PersonName</a>
                     }
                     <span class="text-muted small">@album.AssetCount assets</span>
@@ -142,7 +142,7 @@
             </div>
         </div>
 
-        @if (album.Images.Count == 0) {
+        @if (album!.Images.Count == 0) {
             <EmptyState Variant="info" Title="No assets in this album" />
         } else {
             <div class="@("album-assets-grid " + viewMode)">

MilkStream.Client/Components/Pages/CosplayerDetail.razor

@@ -59,7 +59,7 @@
                             <span class="text-muted small">@pub public, @prot protected, @priv private</span>
                         }
                         <span class="mx-1">·</span>
-                        <span><i class="bi bi-image"></i> @person.TotalAssets assets</span>
+                        <span><i class="bi bi-image"></i> @person!.TotalAssets assets</span>
                         @if (person.MaintainerUserIds?.Count > 0)
                         {
                             <span class="mx-1">·</span>

MilkStream.Client/Components/Pages/Home.razor

@@ -248,6 +248,7 @@
     }
 
     void NavigatePreview(int direction) {
+        if (selectedAsset == null) return;
         var newIndex = selectedIndex + direction;
         if (newIndex < 0 || newIndex >= flatList.Count) return;
         var newAsset = flatList[newIndex];