CSV bulk miner import

Please consider adding CSV-based bulk miner import.

Use case: we often already have miner details in a spreadsheet before deployment or migration. It would be helpful to upload a CSV and create/stage miners instead of relying only on Pickaxe discovery.

Helpful fields:

• IP address
• MAC address
• Worker name
• Site/location
• Rack/slot
• Model
• Serial number

Ideally, Foreman could validate the CSV, flag duplicates/errors, and let Pickaxe resync the miners afterward.