feat(telegram-chat-bot): implement AI chat bot with multi-model support

- Add NestJS service with Telegraf for Telegram bot
- Implement commands: /models, /model, /new, /convos, /history, /clear
- Create Chat API client for completions and conversations
- Support multiple AI models (local Gemma + cloud via OpenRouter)
- Sync conversations with Chat web/mobile app
- Add message splitting for long responses
- Include Dockerfile, CLAUDE.md, and setup script

Commands:
- Send text → AI responds
- /models - List available models
- /model [name] - Switch model (gemma, claude, gpt, etc.)
- /new [title] - New conversation
- /convos - List conversations
- /history - Show recent messages
- /clear - Clear context

https://claude.ai/code/session_01LwmhvhKpEsvVtY1ZKhYu6f

docs/TELEGRAM_BOTS.md

@@ -11,6 +11,7 @@ Dokumentation aller Telegram-Bots im ManaCore Monorepo.
 | [telegram-project-doc-bot](#telegram-project-doc-bot) | 3302 | Projektdokumentation & Blogpost-Generierung | ✅ Aktiv |
 | [telegram-calendar-bot](#telegram-calendar-bot) | 3303 | Kalender-Termine & Erinnerungen | 🚧 In Entwicklung |
 | [telegram-contacts-bot](#telegram-contacts-bot) | 3304 | Kontaktsuche & Geburtstags-Erinnerungen | 🚧 In Entwicklung |
+| [telegram-chat-bot](#telegram-chat-bot) | 3305 | AI-Chat mit verschiedenen Modellen | 🚧 In Entwicklung |
 
 ## Gemeinsame Architektur