feat(channels): add mattermost adapter and wiring

README.md

@@ -6,7 +6,7 @@ Self-hosted personal AI assistant with Telegram and Terminal interfaces.
 
 - **Multi-Frontend**: Telegram bot + Terminal UI (minimal & fullscreen modes) + Web UI dashboard
 - **Multi-Model**: Anthropic Claude, OpenAI, GitHub Copilot, Gemini, Bedrock, Zhipu AI (GLM), xAI (Grok), Ollama, llama.cpp with intelligent routing
-- **Multi-Channel**: Telegram, Discord, Slack, WhatsApp, Matrix, Signal, Microsoft Teams, Google Chat, and iMessage (BlueBubbles) with unified adapter interface
+- **Multi-Channel**: Telegram, Discord, Slack, WhatsApp, Matrix, Signal, Mattermost, Microsoft Teams, Google Chat, and iMessage (BlueBubbles) with unified adapter interface
 - **Web Dashboard**: SPA control panel with health monitoring, chat, session browser, usage stats, and settings editor
 - **Model Switching**: Switch between cloud/local models on demand
 - **Session Persistence**: SQLite-backed conversation history
@@ -161,6 +161,15 @@ teams:
 # Bot Framework messaging endpoint should point to:
 # POST https://<your-flynn-host>/teams/events
 
+# Optional: Mattermost
+mattermost:
+  server_url: "${MATTERMOST_SERVER_URL}"
+  bot_token: "${MATTERMOST_BOT_TOKEN}"
+  allowed_channel_ids: []  # Recommended: explicit channel IDs
+  require_mention: true
+  mention_name: "flynn"
+  poll_interval_ms: 3000
+
 # Optional: Google Chat
 google_chat:
   service_account_key_file: "~/.config/flynn/google-chat-service-account.json"