fix(online): green-felt freeze — replay initial state to late subscriber

Root cause: the server sends matchFound then immediately broadcasts the first
state, but the client only subscribes to state inside enterServerMatch, which
runs a React effect later — so the ordered "state" message is dispatched while
there are no subscribers and is dropped. The server then waits for the human
hakem's trump choice that can never come → permanent freeze on the green felt.

- signalr-service: cache lastState; replay it to a late onState subscriber on a
  microtask (after enterServerMatch resets its store); clear the cache on every
  fresh-match entry (startMatchmaking / createRoom / acceptInvite) so a finished
  game's final state is never replayed into a new match.
- safety net: if no state lands within 2.5s of matchFound, the client invokes
  the new Resync hub method; server re-sends the current state to that player.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

server/src/Hokm.Server/Game/GameManager.cs

@@ -81,6 +81,13 @@ public sealed partial class GameManager
         }
     }
 
+    /// <summary>Client safety net: re-send the current game state to a player who
+    /// may have missed the initial broadcast (green-felt freeze guard).</summary>
+    public void Resync(string userId)
+    {
+        if (RoomOf(userId) is { } room) room.ResendStateTo(userId);
+    }
+
     /// <summary>Player asked to start right now — match any humans waiting and
     /// fill the rest with bots, instead of waiting out the queue.</summary>
     public void PlayNow(string userId)

server/src/Hokm.Server/Game/GameRoom.cs

@@ -387,6 +387,19 @@ public sealed class GameRoom : IDisposable
             _ = _hub.Clients.User(slot.UserId!).SendAsync("state", ToDto(slot.Seat));
     }
 
+    /// <summary>Re-send the current state to one player on demand — the client's
+    /// safety net when the initial broadcast was dropped/raced and the table
+    /// would otherwise freeze waiting for a state that never arrived.</summary>
+    public void ResendStateTo(string userId)
+    {
+        lock (_lock)
+        {
+            var slot = Seats.FirstOrDefault(s => !s.IsBot && s.UserId == userId);
+            if (slot != null)
+                _ = _hub.Clients.User(userId).SendAsync("state", ToDto(slot.Seat));
+        }
+    }
+
     private void Broadcast(string method, object payload)
     {
         foreach (var slot in Seats.Where(s => !s.IsBot && s.UserId != null && s.Connected))

server/src/Hokm.Server/Hubs/GameHub.cs

@@ -38,6 +38,7 @@ public sealed class GameHub : Hub
 
     public void CancelMatchmaking() => _manager.CancelMatchmaking(Uid);
     public void PlayNow() => _manager.PlayNow(Uid);
+    public void Resync() => _manager.Resync(Uid);
     public void PlayCard(string cardId) => _manager.PlayCard(Uid, cardId);
     public void ChooseTrump(string suit) => _manager.ChooseTrump(Uid, suit);
     public void SendReaction(string reaction) => _manager.SendReaction(Uid, reaction);