feat(plugin): add ReMe integration for QwenPaw

**Background**

QwenPaw needs a native ReMe integration for persistent memory across assistant sessions. The repository currently includes a standalone `qwenpaw_memory` file convention, while the recommended ReMe path is to embed the Python SDK. A dedicated plugin should make that integration installable and keep user-owned ReMe workspace files as the source of truth.

**Changes**
- Add an installable QwenPaw plugin under `plugins/qwenpaw`
- Embed ReMe through the Python SDK and align its lifecycle with the QwenPaw application
- Map QwenPaw conversations and profiles to stable ReMe session and user boundaries
- Add recall before relevant responses and non-blocking durable memory recording after useful turns
- Support automatic memory consolidation and proactive memory workflows through QwenPaw scheduling
- Keep the existing direct-file `qwenpaw_memory` convention clearly separated from the ReMe-backed integration
- Add configuration, installation documentation, and focused lifecycle and memory tests