<instructions>
Implement this specification as clean, production-grade code.
</instructions>

<context>
  <document path="docs/auth-middleware.md">
    # Authentication Middleware Specification
    
    The application enforces JWT-based authentication across all API endpoints under `/api/v1/*`.
    
    ## Requirements
    - Validate the `Authorization: Bearer <token>` header.
    - If expired or invalid, return HTTP 401 Unauthorized with error code `AUTH_TOKEN_EXPIRED`.
    - Extract user roles (`admin`, `member`, `viewer`) and attach to request context.
    
    ### Example Token Payload:
    ```json
    {
      "sub": "usr_9482918",
      "email": "dev@company.com",
      "role": "admin",
      "exp": 1726000000
    }
    ```
    
    ## Edge Cases:
    1. Missing Authorization header completely.
    2. Malformed token string without the Bearer prefix.
  </document>
</context>

<task>
Please proceed with the implementation, adhering strictly to the provided context and requirements.
</task>