fix(data): align portfolio mutation lock order

src/GmRelay.AppHost/Program.cs

@@ -6,7 +6,9 @@ var postgres = builder.AddPostgres("postgres")
 
 var bot = builder.AddProject<Projects.GmRelay_Bot>("bot")
     .WithReference(postgres)
-    .WaitFor(postgres);
+    .WaitFor(postgres)
+    .WithHttpEndpoint(port: 8081, targetPort: 8081, name: "health")
+    .WithHttpHealthCheck("/health", endpointName: "health");
 
 builder.AddProject<Projects.GmRelay_DiscordBot>("discord")
     .WithReference(postgres)

src/GmRelay.DiscordBot/Features/Sessions/DiscordDeleteSessionHandler.cs

@@ -45,6 +45,19 @@ public sealed class DiscordDeleteSessionHandler(
         }
 
         await using var transaction = await connection.BeginTransactionAsync(cancellationToken);
+        _ = await connection.QuerySingleOrDefaultAsync<Guid?>(
+            """
+            SELECT s.id
+            FROM sessions s
+            JOIN game_groups g ON g.id = s.group_id
+            WHERE s.id = @SessionId
+              AND g.platform = 'Discord'
+              AND g.external_group_id = @GuildId
+            FOR UPDATE OF s
+            """,
+            new { SessionId = sessionId, GuildId = guildId },
+            transaction);
+
         await connection.ExecuteAsync(
             """
             UPDATE portfolio_games pg

src/GmRelay.Shared/Features/Sessions/ListSessions/DeleteSessionHandler.cs

@@ -31,7 +31,7 @@ public sealed class DeleteSessionHandler(
         await using var connection = await dataSource.OpenConnectionAsync(ct);
         await using var transaction = await connection.BeginTransactionAsync(ct);
 
-        // 1. Fetch session and verify group manager.
+        // 1. Lock the session before any linked portfolio card and verify group manager.
         var session = await connection.QuerySingleOrDefaultAsync<DeleteSessionInfoDto>(
             """
             SELECT s.title AS Title,
@@ -49,6 +49,7 @@ public sealed class DeleteSessionHandler(
                    ) AS CanManage
             FROM sessions s
             WHERE s.id = @SessionId
+            FOR UPDATE OF s
             """,
             new { command.SessionId, Platform = command.User.Platform.ToString(), ExternalUserId = command.User.ExternalUserId }, transaction);