feat(matrix-chat-bot): add Matrix bot for AI chat conversations

- Quick chat mode for stateless single messages (!chat)
- Full conversation management (create, list, select, delete)
- Message history with context-aware AI responses
- Model selection (Ollama, OpenRouter, OpenAI, Anthropic)
- Conversation actions: archive, restore, pin, unpin, rename
- German/English command aliases
- Number-based reference system for ease of use
- JWT auth via mana-core-auth
- Health check endpoint on port 3327

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

services/matrix-chat-bot/.env.example

@@ -0,0 +1,15 @@
+# Server
+PORT=3327
+
+# Matrix
+MATRIX_HOMESERVER_URL=http://localhost:8008
+MATRIX_ACCESS_TOKEN=syt_xxx
+MATRIX_ALLOWED_ROOMS=#chat:matrix.mana.how
+MATRIX_STORAGE_PATH=./data/bot-storage.json
+
+# Chat Backend
+CHAT_BACKEND_URL=http://localhost:3002
+CHAT_API_PREFIX=
+
+# Mana Core Auth
+MANA_CORE_AUTH_URL=http://localhost:3001