Feature Request: Matrix integration for notifications and real-time communication in Huly Chat

### Summary

Add support for the [Matrix](https://matrix.org/) protocol to enable real-time messaging and notifications directly from Huly. This would allow teams to receive updates on tasks, documents, mentions, and other events in Matrix rooms (e.g., via Element or other clients).

### Motivation

Matrix is widely used in open-source and privacy-conscious teams. This integration would make Huly more accessible to communities already relying on Matrix for communication, reducing context-switching and improving response times.

### Proposed Features

- **Configuration**: Allow users to set Matrix homeserver URL and access token in workspace settings.
- **Project-to-room mapping**: Link Huly projects or spaces to specific Matrix rooms.
- **Event notifications**:
- Task created / assigned / updated / closed
- Document changes
- Mentions
- **Rich messages**: Use markdown formatting and optionally interactive buttons for quick actions.
- **Bot commands** (optional): Allow `/huly new-task "Title"` or `/huly status TASK-123` directly from Matrix.
- **E2E encryption** (optional): Support end-to-end encryption via Matrix SDK.

### Acceptance Criteria

- [ ] Settings UI to configure Matrix homeserver and token.
- [ ] Ability to map one or more Huly projects/spaces to Matrix rooms.
- [ ] Real-time notifications for key events (task changes, mentions, document edits).
- [ ] Documentation and example webhook payloads.

### Additional Context

- Matrix JS SDK: [matrix-js-sdk](https://github.com/matrix-org/matrix-js-sdk) for Node/Browser.
- List of all supported Matrix SDKs: [matrix-sdks](https://matrix.org/ecosystem/sdks/)