```python
from collections import deque
from typing import Optional

class JobQueue:
    def __init__(self):
        self._queue: deque = deque()
        self._results: dict = {}

    def add_job(self, job_id: str, data: dict) -> str:
        job = {
            'job_id': job_id,
            'data': data,
            'status': 'pending',
            'result': None
        }
        self._queue.append(job)
        self._results[job_id] = job
        return job_id

    def get_result(self, job_id: str) -> dict | None:
        if job_id in self._results:
            job = self._results[job_id]
            if job['status'] == 'completed':
                return job['result']
        return None

    def process(self):
        while self._queue:
            job = self._queue.popleft()
            job['status'] = 'completed'
            job['result'] = {'status': 'success', 'data': job['data']}
            self._results[job['job_id']] = job
```