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>

.gitignore

@@ -39,3 +39,9 @@ yarn-error.log*
 # typescript
 *.tsbuildinfo
 next-env.d.ts
+
+# .NET (server/)
+[Bb]in/
+[Oo]bj/
+*.user
+