feat(CF-1189): Add AI text bot + WildFiles RAG integration

Extends bot.py with text message handling:
- RoomMessageText callback with @mention detection
- LLM responses via LiteLLM (OpenAI-compatible)
- WildFiles document search (DocumentRAG class)
- Per-room model selection via room state events
- Commands: !ai help/models/set-model/search
- Typing indicators during AI response generation
- 30s staleness check to avoid replaying history

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

docker-compose.yml

@@ -11,6 +11,12 @@ services:
     command: python bot.py
     env_file: .env
     restart: unless-stopped
+    environment:
+      - LITELLM_BASE_URL
+      - LITELLM_API_KEY
+      - DEFAULT_MODEL
+      - WILDFILES_BASE_URL
+      - WILDFILES_ORG
     volumes:
       - bot-crypto:/data/crypto_store