feat: Add presence heartbeat for Matrix online status

- matrix-gateway: POST /internal/matrix/presence/online endpoint
- usePresenceHeartbeat hook with activity tracking
- Auto away after 5 min inactivity
- Offline on page close/visibility change
- Integrated in MatrixChatRoom component

services/llm-proxy/providers/__init__.py

@@ -0,0 +1,10 @@
+from .base_provider import BaseProvider
+from .openai_provider import OpenAIProvider
+from .deepseek_provider import DeepSeekProvider
+from .local_provider import LocalProvider
+
+__all__ = ['BaseProvider', 'OpenAIProvider', 'DeepSeekProvider', 'LocalProvider']
+
+
+
+