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/Controllers/Notify/NotifyController.cs

@@ -0,0 +1,21 @@
+using Microsoft.AspNetCore.Mvc;
+
+namespace DorkNet.Server.Controllers.Notify;
+
+/// <summary>
+/// notify.rec.net — legacy raw-WebSocket entrypoint that the 2020 client
+/// briefly used before switching to the SignalR hub at
+/// <c>notify.rec.net/hub/v1</c>. Kept as a 410 Gone so any straggling
+/// boot path that hits it gets a clear "use the hub" signal instead of
+/// a silent connection upgrade.
+/// </summary>
+[ApiController]
+public class NotifyController : ControllerBase
+{
+    [HttpGet("/notify/v1")]
+    public IActionResult Connect() => StatusCode(StatusCodes.Status410Gone, new
+    {
+        error = "use_signalr_hub",
+        hint = "connect to /hub/v1 instead",
+    });
+}