Phase G: scaffold .NET 10 + SignalR backend (engine port + hub + auth)

- server/ monorepo: Hokm.Engine (C# port of TS engine+AI, validated by sim),
  Hokm.Server (SignalR GameHub, in-memory matchmaking/rooms, server-side turn
  timers + bot fill + disconnect handling, per-seat state broadcast), Hokm.Sim
- JWT dev auth (OTP 1234 + email); CORS for the Next client; /hub/game
- NuGet restored from mirrors (Soroush Nexus + Liara); NuGetAudit off
- README + .NET .gitignore; static class Engine renamed Rules (namespace clash)

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

server/NuGet.config

@@ -0,0 +1,10 @@
+<?xml version="1.0" encoding="utf-8"?>
+<configuration>
+  <packageSources>
+    <clear />
+    <!-- Soroush self-hosted Nexus group -->
+    <add key="soroush-nexus" value="https://mirror.soroushasadi.com/repository/nuget-group/index.json" protocolVersion="3" />
+    <!-- Liara public mirror -->
+    <add key="liara" value="https://package-mirror.liara.ir/repository/nuget/index.json" protocolVersion="3" />
+  </packageSources>
+</configuration>