feat(social): friends list resolution + fix ping request 500

- RequestUsersPingRequest: the client sends ping=2147483648 (int.MaxValue+1)
  for "no ping", which overflowed the int field and made every ping request
  return 500. Widened to long.
- ClientsideFriendsImport: persist the imported Steam friend ids per user.
- GetFriendList: resolve those ids to the players that exist on this server
  (batch lookup by Steam auth key) and return them as friends. Response
  shape is best-effort pending in-game confirmation.
- DbUserService.FindManyAsync: batch-resolve auth keys to players.

First step of the station lobby (see friends on the server). Squad
formation / invite flow to follow once friends are visible.

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

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

@@ -1,15 +1,71 @@
-using Prospect.Server.Api.Services.CloudScript.Models;
+using System.Text.Json;
+using Prospect.Server.Api.Services.Auth.Extensions;
+using Prospect.Server.Api.Services.CloudScript.Models;
+using Prospect.Server.Api.Services.Database;
+using Prospect.Server.Api.Services.Database.Models;
+using Prospect.Server.Api.Services.UserData;
 
 namespace Prospect.Server.Api.Services.CloudScript.Functions;
 
 [CloudScriptFunction("GetFriendList")]
 public class GetFriendList : ICloudScriptFunction<FYBaseSocialRequest, object?>
 {
-    public Task<object?> ExecuteAsync(FYBaseSocialRequest request)
+    private readonly ILogger<GetFriendList> _logger;
+    private readonly IHttpContextAccessor _httpContextAccessor;
+    private readonly UserDataService _userDataService;
+    private readonly DbUserService _userService;
+
+    public GetFriendList(ILogger<GetFriendList> logger, IHttpContextAccessor httpContextAccessor, UserDataService userDataService, DbUserService userService)
     {
-        return Task.FromResult<object?>(new
-        {
-            
-        });
+        _logger = logger;
+        _httpContextAccessor = httpContextAccessor;
+        _userDataService = userDataService;
+        _userService = userService;
     }
-}
+
+    public async Task<object?> ExecuteAsync(FYBaseSocialRequest request)
+    {
+        var context = _httpContextAccessor.HttpContext;
+        if (context == null)
+        {
+            throw new CloudScriptException("CloudScript was not called within a http request");
+        }
+        var userId = context.User.FindAuthUserId();
+
+        // Resolve the imported Steam friends (persisted by ClientsideFriendsImport) to the
+        // players that actually exist on this server. It's a private server, so only friends
+        // who have logged in here will show up.
+        var steamIds = new List<string>();
+        var userData = await _userDataService.FindAsync(userId, userId, new List<string> { "ImportedSteamFriends" });
+        if (userData.TryGetValue("ImportedSteamFriends", out var rec) && !string.IsNullOrWhiteSpace(rec.Value))
+        {
+            try { steamIds = JsonSerializer.Deserialize<List<string>>(rec.Value) ?? new List<string>(); }
+            catch { /* ignore malformed */ }
+        }
+
+        var friends = new List<object>();
+        if (steamIds.Count > 0)
+        {
+            var players = await _userService.FindManyAsync(PlayFabUserAuthType.Steam, steamIds);
+            foreach (var player in players)
+            {
+                if (player.Id == userId) continue; // never list yourself
+                friends.Add(new
+                {
+                    profile = new
+                    {
+                        playerId = player.Id,
+                        displayName = player.DisplayName,
+                        avatarUrl = "",
+                    },
+                    onlineState = 0, // EYUserState — real presence tracking is a later phase
+                });
+            }
+        }
+
+        // NOTE: the exact response shape the client expects is not yet confirmed; this is a
+        // best-effort structure. The log lets us verify resolution while we validate in game.
+        _logger.LogInformation("GetFriendList for {User}: {Count} friend(s) resolved on server", userId, friends.Count);
+        return new { friends };
+    }
+}