feat(squad): in-memory squad/lobby state + wire squad functions

Adds SquadService (singleton, process-local) tracking squads by the
squadId the client shares across party members, plus a user->squad index
so TryGetCompleteSquadInfo (no squadId in request) can resolve the
caller's squad. Members are lazily registered on any squad call.

- TryGetCompleteSquadInfo: returns the caller's real squad.
- SquadMemberReadyForMatch: joins the squad, records readiness/map,
  returns the squad + whether everyone is ready.
- SquadMemberSelectedMap: records the member's selected map.
- DbUserService.FindByIdAsync: resolve display name for squad members.

Groundwork for the station lobby; assumes the client drives squads via
these calls with a shared squadId (to confirm with a 2-client session).
Real-time SignalR push (unknown event names) deferred; the squad is
carried in responses + TryGetCompleteSquadInfo for now.

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

src/Prospect.Server.Api/Services/CloudScript/Functions/TryGetCompleteSquadInfo.cs

@@ -1,5 +1,8 @@
 using System.Text.Json.Serialization;
+using Prospect.Server.Api.Services.Auth.Extensions;
 using Prospect.Server.Api.Services.CloudScript;
+using Prospect.Server.Api.Services.Database;
+using Prospect.Server.Api.Services.Squad;
 
 public class TryGetCompleteSquadInfoRequest
 {
@@ -51,26 +54,30 @@ public class TryGetCompleteSquadInfoFunction : ICloudScriptFunction<TryGetComple
 {
     private readonly ILogger<TryGetCompleteSquadInfoFunction> _logger;
     private readonly IHttpContextAccessor _httpContextAccessor;
+    private readonly SquadService _squadService;
 
-    public TryGetCompleteSquadInfoFunction(ILogger<TryGetCompleteSquadInfoFunction> logger, IHttpContextAccessor httpContextAccessor)
+    public TryGetCompleteSquadInfoFunction(ILogger<TryGetCompleteSquadInfoFunction> logger, IHttpContextAccessor httpContextAccessor, SquadService squadService)
     {
         _httpContextAccessor = httpContextAccessor;
         _logger = logger;
+        _squadService = squadService;
     }
 
-    public async Task<FYPlayFabSquad> ExecuteAsync(TryGetCompleteSquadInfoRequest request)
+    public Task<FYPlayFabSquad> ExecuteAsync(TryGetCompleteSquadInfoRequest request)
     {
         var context = _httpContextAccessor.HttpContext;
         if (context == null)
         {
             throw new CloudScriptException("CloudScript was not called within a http request");
         }
-        // var userId = context.User.FindAuthUserId();
-
-        return new FYPlayFabSquad
+        var userId = context.User.FindAuthUserId();
+        var squad = _squadService.GetByUser(userId);
+        if (squad == null)
         {
-            // SquadID = "100",
-            // Members = [],
-        };
+            // Not in a squad yet — return an empty squad (same as the previous stub).
+            return Task.FromResult(new FYPlayFabSquad());
+        }
+        _logger.LogInformation("TryGetCompleteSquadInfo: user {User} in squad {Squad} ({Count} member(s))", userId, squad.SquadId, squad.Members.Count);
+        return Task.FromResult(_squadService.ToClientSquad(squad));
     }
 }