fix(matchmaking): deploy signal targets only the deploying player

EnterMatchmakingMatch broadcast OnSquadMatchmakingSuccess to Clients.All,
so one player deploying pulled every connected player into the match.
Map each player to their SignalR connection (GetSignalRConnection tags the
URL with uid; CycleHub records it via a SignalRConnectionRegistry) and
send the deploy signal only to that connection (broadcast fallback if
unmapped). Also enable m_automaticImportPlatformFriends (Steam friends).

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

src/Prospect.Server.Api/Hubs/CycleHub.cs

@@ -1,12 +1,31 @@
-using Microsoft.AspNetCore.SignalR;
+using Microsoft.AspNetCore.SignalR;
 
 namespace Prospect.Server.Api.Hubs;
 
 public class CycleHub : Hub
 {
+    private readonly SignalRConnectionRegistry _registry;
+
+    public CycleHub(SignalRConnectionRegistry registry)
+    {
+        _registry = registry;
+    }
+
     public override async Task OnConnectedAsync()
     {
-        Console.WriteLine("Connected {0}", Context.ConnectionId);
+        // The client connects with the SignalR URL returned by GetSignalRConnection, which
+        // carries a `uid` query param — use it to map this connection to the player so
+        // server-initiated messages can target a single player instead of everyone.
+        var uid = Context.GetHttpContext()?.Request.Query["uid"].ToString();
+        if (!string.IsNullOrEmpty(uid))
+            _registry.Add(uid, Context.ConnectionId);
+        Console.WriteLine("Connected {0} (uid={1})", Context.ConnectionId, uid);
         await base.OnConnectedAsync();
     }
-}
+
+    public override async Task OnDisconnectedAsync(Exception? exception)
+    {
+        _registry.Remove(Context.ConnectionId);
+        await base.OnDisconnectedAsync(exception);
+    }
+}

src/Prospect.Server.Api/Hubs/SignalRConnectionRegistry.cs

@@ -0,0 +1,29 @@
+using System.Collections.Concurrent;
+
+namespace Prospect.Server.Api.Hubs;
+
+// Maps players to their live SignalR connection so server-initiated messages (e.g. the
+// matchmaking-success "travel to match" signal) can target a single player instead of being
+// broadcast to everyone. The client's SignalR URL carries a `uid` query param (added by
+// GetSignalRConnection); CycleHub records it on connect.
+public class SignalRConnectionRegistry
+{
+    private readonly ConcurrentDictionary<string, string> _userToConn = new();
+    private readonly ConcurrentDictionary<string, string> _connToUser = new();
+
+    public void Add(string userId, string connectionId)
+    {
+        if (string.IsNullOrEmpty(userId)) return;
+        _userToConn[userId] = connectionId;
+        _connToUser[connectionId] = userId;
+    }
+
+    public void Remove(string connectionId)
+    {
+        if (_connToUser.TryRemove(connectionId, out var userId))
+            _userToConn.TryRemove(userId, out _);
+    }
+
+    public string? GetConnection(string userId)
+        => _userToConn.TryGetValue(userId, out var c) ? c : null;
+}