feat: support co-gm group delegation

src/GmRelay.Bot/Features/Sessions/RescheduleSession/InitiateRescheduleHandler.cs

@@ -16,7 +16,7 @@ public sealed record InitiateRescheduleCommand(
 
 // ── DTOs ─────────────────────────────────────────────────────────────
 
-internal sealed record RescheduleSessionInfoDto(string Title, long GmId);
+internal sealed record RescheduleSessionInfoDto(string Title, bool CanManage);
 
 // ── Handler ──────────────────────────────────────────────────────────
 
@@ -34,15 +34,21 @@ public sealed class InitiateRescheduleHandler(
     {
         await using var connection = await dataSource.OpenConnectionAsync(ct);
 
-        // 1. Verify GM ownership
+        // 1. Verify group management access.
         var session = await connection.QuerySingleOrDefaultAsync<RescheduleSessionInfoDto>(
             """
-            SELECT s.title AS Title, g.gm_telegram_id AS GmId
+            SELECT s.title AS Title,
+                   EXISTS (
+                       SELECT 1
+                       FROM group_managers gm
+                       JOIN players p ON p.id = gm.player_id
+                       WHERE gm.group_id = s.group_id
+                         AND p.telegram_id = @TelegramUserId
+                   ) AS CanManage
             FROM sessions s
-            JOIN game_groups g ON s.group_id = g.id
             WHERE s.id = @SessionId AND s.status != @Cancelled
             """,
-            new { command.SessionId, Cancelled = SessionStatus.Cancelled });
+            new { command.SessionId, command.TelegramUserId, Cancelled = SessionStatus.Cancelled });
 
         if (session is null)
         {
@@ -50,10 +56,10 @@ public sealed class InitiateRescheduleHandler(
             return;
         }
 
-        if (session.GmId != command.TelegramUserId)
+        if (!session.CanManage)
         {
             await bot.AnswerCallbackQuery(command.CallbackQueryId,
-                "Только Мастер Игры (GM) может переносить сессию.", showAlert: true, cancellationToken: ct);
+                "Только owner или co-GM может переносить сессию.", showAlert: true, cancellationToken: ct);
             return;
         }