Import december-2020-12-18 from private repo (scrubbed 2026-05-27)

Targets Rec Room 2020.12.18 client.

Re-import after adding:
- DorkNet.ClientMod/dorknet-clientmod.json.template — config schema
  the launcher's manifest-driven patcher renders into UserData/.
- tools/build-patcher-zip.ps1 — produces the dorknet-clientpatch-{key}.zip
  Release asset the launcher fetches.
- .github/workflows/release.yml — auto-publishes both Release assets
  on v1-december-* tag push.

Scrubbed via maintainer-side scrub-for-public.ps1: same drop rules as
the prior import, plus build-patcher-zip.ps1 added to the tools/
allow-list so it survives the scrub.

DorkNet.Server/Data/Entities/PlaylistRoomEntity.cs

@@ -0,0 +1,14 @@
+namespace DorkNet.Server.Data.Entities;
+
+/// <summary>
+/// Links a <see cref="PlaylistEntity"/> to one of its member rooms. The
+/// playlist's room ordering is driven by <see cref="OrderIndex"/> so a
+/// curator can promote/demote entries without renumbering rows.
+/// </summary>
+public class PlaylistRoomEntity
+{
+    public long Id { get; set; }
+    public long PlaylistId { get; set; }
+    public long RoomId { get; set; }
+    public int OrderIndex { get; set; } = 0;
+}