feat: Enhance task and reward assignment logic to prioritize user items over system items with the same name; add corresponding tests

.github/copilot-instructions.md

@@ -15,6 +15,7 @@
 - **Scoped Styles**: All `.vue` files must use `<style scoped>`. Reference global variables for theme consistency.
 - **API Error Handling**: Backend returns JSON with `error` and `code` (see `backend/api/error_codes.py`). Frontend extracts `{ msg, code }` using `parseErrorResponse(res)` from `api.ts`.
 - **JWT Auth**: Tokens are stored in HttpOnly, Secure, SameSite=Strict cookies.
+- **Code Style**: Follow PEP 8 for Python, and standard TypeScript conventions. Use type annotations everywhere in Python. Place python changes after imports. Place all imports at the top of the file.
 
 ## 🚦 Frontend Logic & Event Bus
 
@@ -29,6 +30,7 @@
 ## 🛠️ Developer Workflows
 
 - **Backend**: Run Flask with `python -m flask run --host=0.0.0.0 --port=5000` from the `backend/` directory. Main entry: `backend/main.py`.
+- **Virtual Env**: Python is running from a virtual environment located at `backend/.venv/`.
 - **Frontend**: From `frontend/vue-app/`, run `npm install` then `npm run dev`.
 - **Tests**: Run backend tests with `pytest` in `backend/tests/`. Frontend component tests: `npm run test` in `frontend/vue-app/components/__tests__/`.
 - **Debugging**: Use VS Code launch configs or run Flask/Vue dev servers directly. For SSE, use browser dev tools to inspect event streams.