Implement Watcher Functionality

Based on: https://github.com/aai-institute/infrastructure-product/pull/30

## Objective
Convert the existing standalone watcher application into an API endpoint within our existing backend service, allowing for more integrated job lifecycle notifications.

## User Story
As a user, I want to receive notifications about my job's lifecycle events through the same API that I use to submit and manage jobs, so that I can have a more unified and streamlined experience. This allows real-time streaming of the job lifecycle.

## Requirements

1. Create a new endpoint `/jobs/{uid}/watch` in the existing FastAPI backend.
2. Implement functionality for real-time updates.