feat(player): add append-only "Add to Queue" buttons beside detail-page play affordances

Cut header (release → EnqueueRange), Cut track rows + Session/Mix hero (track → Enqueue). Reuses existing engine path; add is not play.

DeepDrftPublic.Client/Pages/CutDetail.razor

@@ -94,6 +94,10 @@ else
                             Play
                         </MudButton>
 
+                        @* Append the whole album (TrackNumber order) to the queue — same ordered list
+                           header Play uses. Append-only: does not start playback (AC7/AC8). *@
+                        <AddToQueueButton ReleaseTracks="@ViewModel.Tracks" />
+
                         @* Release-mode share: copies the canonical /cuts/{entryKey} URL, not a single track (§3b). *@
                         <SharePopover ReleaseEntryKey="@release.EntryKey" ReleaseMedium="@release.Medium" />
                     </div>
@@ -138,6 +142,8 @@ else
                                                OnToggle="@(() => PlayTrack(track, index))" />
                             </div>
                             <span class="cut-detail-track-name text-truncate">@track.TrackName</span>
+                            @* Append this single track to the queue (append-only, does not play). *@
+                            <AddToQueueButton Track="@track" />
                             <SharePopover EntryKey="@track.EntryKey" />
                         </div>
                     }

DeepDrftPublic.Client/Pages/MixDetail.razor

@@ -81,6 +81,8 @@ else
                         @if (ViewModel.Track is not null)
                         {
                             <PlayStateIcon Track="@ViewModel.Track" Size="Size.Large" Color="Color.Secondary" OnToggle="@PlayTrack" />
+                            @* Append-only: queues the mix's single track without starting playback. *@
+                            <AddToQueueButton Track="@ViewModel.Track" Size="Size.Large" />
                         }
                     </PlayContent>
                 </ReleaseHeroOverlay>

DeepDrftPublic.Client/Pages/SessionDetail.razor

@@ -79,6 +79,8 @@ else
                 @if (ViewModel.Track is not null)
                 {
                     <PlayStateIcon Track="@ViewModel.Track" Size="Size.Large" Color="Color.Secondary" OnToggle="@PlayTrack" />
+                    @* Append-only: queues the session's single track without starting playback. *@
+                    <AddToQueueButton Track="@ViewModel.Track" Size="Size.Large" />
                 }
             </PlayContent>
         </ReleaseHeroOverlay>