refactor: завершить platform migration и удалить deprecated telegram_* scaffolding

- Добавлены миграции V024 (backfill + deprecation comments + calendar_subscriptions platform identity) и V025 (backfill proposed_by_external_user_id)
- Все Bot handlers переведены с telegram_id/chat_id на platform + external_*
- Shared handlers очищены от COALESCE fallback с telegram_* колонками
- DiscordBot очищен от COALESCE fallback
- Web SessionService и CalendarSubscriptionService переведены на external_*
- HandleRsvpHandler: убран legacy UNION с gm_telegram_id, теперь только group_managers
- RescheduleVotingFinalizer: переведен на external_username/external_user_id
- Tests: добавлены asserts для V024/V025
- Версия обновлена до 3.1.0

Bump version → 3.1.0

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

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

@@ -53,26 +53,28 @@ public sealed class HandleRescheduleTimeInputHandler(
             """
             SELECT rp.id AS Id, rp.session_id AS SessionId, s.title AS Title, s.scheduled_at AS CurrentScheduledAt,
                    s.batch_id AS BatchId, s.batch_message_id AS BatchMessageId,
-                   g.telegram_chat_id AS TelegramChatId,
+                   g.external_group_id::BIGINT AS TelegramChatId,
                    s.thread_id AS ThreadId,
                    s.notification_mode AS NotificationMode
             FROM reschedule_proposals rp
             JOIN sessions s ON s.id = rp.session_id
             JOIN game_groups g ON g.id = s.group_id
-            WHERE rp.proposed_by = @GmId
+            WHERE rp.proposed_by_external_user_id = @ExternalGmId
               AND rp.status = 'AwaitingTime'
-              AND g.telegram_chat_id = @ChatId
+              AND g.platform = 'Telegram'
+              AND g.external_group_id = @ExternalChatId
               AND EXISTS (
                   SELECT 1
                   FROM group_managers gm
                   JOIN players manager_player ON manager_player.id = gm.player_id
                   WHERE gm.group_id = s.group_id
-                    AND manager_player.telegram_id = @GmId
+                    AND manager_player.platform = 'Telegram'
+                    AND manager_player.external_user_id = @ExternalGmId
               )
             ORDER BY rp.created_at DESC
             LIMIT 1
             """,
-            new { GmId = gmTelegramId, ChatId = chatId });
+            new { ExternalGmId = gmTelegramId.ToString(), ExternalChatId = chatId.ToString() });
 
         if (proposal is null)
             return false;
@@ -92,8 +94,8 @@ public sealed class HandleRescheduleTimeInputHandler(
             """
             SELECT p.id AS PlayerId,
                    p.display_name AS DisplayName,
-                   p.telegram_username AS TelegramUsername,
-                   p.telegram_id AS TelegramId
+                   p.external_username AS TelegramUsername,
+                   p.external_user_id::BIGINT AS TelegramId
             FROM session_participants sp
             JOIN players p ON p.id = sp.player_id
             WHERE sp.session_id = @SessionId
@@ -363,7 +365,7 @@ public sealed class HandleRescheduleTimeInputHandler(
                 """
                 SELECT sp.session_id AS SessionId,
                        p.display_name AS DisplayName,
-                       p.telegram_username AS TelegramUsername,
+                       p.external_username AS TelegramUsername,
                        sp.registration_status AS RegistrationStatus
                 FROM session_participants sp
                 JOIN players p ON sp.player_id = p.id