Add Task Filtering by Status and Priority

[kavyashri-as]

Enable filtering support for the Task Management API.

Scope

• Extend GET /tasks to support optional query parameters: status (pending | completed) and priority (Low | Medium | High)
• Allow filters to be used independently or together
• Maintain backward compatibility

Acceptance Criteria

• GET /tasks?status=pending returns only pending tasks
• GET /tasks?priority=High returns only high-priority tasks
• GET /tasks without filters returns all tasks