feat(#21): support selected telegram topics for schedules

Route new schedules to an existing forum topic when /newsession is sent inside one, create bot-owned topics only from the forum root, and keep group notifications/dashboard updates threaded to the stored topic.

Persist topic ownership so deletion only removes empty bot-created topics, add topic routing tests and smoke coverage, and bump release metadata to 1.14.0.

src/GmRelay.Bot/Features/Reminders/SendJoinLink/SendJoinLinkHandler.cs

@@ -14,6 +14,7 @@ internal sealed record JoinLinkSession(
     string JoinLink,
     DateTime ScheduledAt,
     long TelegramChatId,
+    int? ThreadId,
     string NotificationMode);
 
 internal sealed record ConfirmedPlayer(
@@ -42,6 +43,7 @@ public sealed class SendJoinLinkHandler(
             """
             SELECT s.id, s.title, s.join_link AS JoinLink, s.scheduled_at AS ScheduledAt,
                    g.telegram_chat_id AS TelegramChatId,
+                   s.thread_id AS ThreadId,
                    s.notification_mode AS NotificationMode
             FROM sessions s
             JOIN game_groups g ON g.id = s.group_id
@@ -94,6 +96,7 @@ public sealed class SendJoinLinkHandler(
         // 4. Send
         var message = await bot.SendMessage(
             chatId: session.TelegramChatId,
+            messageThreadId: session.ThreadId,
             text: text,
             cancellationToken: ct);