refactor: extract remaining Telegram handlers to platform-neutral contracts

- Extract CreateSessionHandler, ListSessionsHandler, DeleteSessionHandler,
  ExportCalendarHandler, HandleRescheduleTimeInputHandler,
  HandleRescheduleVoteHandler to GmRelay.Shared
- Add IPlatformMessenger methods: SendScheduleAsync, UpdateScheduleAsync,
  SendGroupMessageAsync with actions, CreateThreadAsync, DeleteThreadAsync
- Rewrite Telegram Bot wrappers as thin adapters delegating to shared handlers
- Rewrite DiscordRescheduleVoteHandler to use shared HandleRescheduleVoteHandler
- Update UpdateRouter with explicit type aliases for ambiguous handler names
- Add contract and source-inspection tests for extracted handlers
- Bump version 3.1.1 → 3.2.0

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

.gitea/workflows/deploy.yml

@@ -6,7 +6,7 @@ on:
       - main 
 
 env:
-  VERSION: 3.1.1
+  VERSION: 3.2.0
 
 jobs:
   # ЧАСТЬ 1: Собираем образы и кладем в Gitea (чтобы делиться с ребятами)