feat(miner): fetch max hash rate, max power and model when creating a miner

[markoceri]

Summary

Lets users fetch device data (max hash rate, max power and model/hostname) from the associated controller while creating a miner, without having to save it first. Previously the "fetch from miner" buttons were only available in edit mode, because the underlying reads operate on a persisted miner.

Backend

• New endpoints GET /miner-controllers/{controller_id}/info and GET /miner-controllers/{controller_id}/limits, backed by MinerActionService.get_controller_info / get_controller_limits, which query a controller directly via a temporary miner (same approach already used by get_miner_details_from_controller).
• Extracted shared _read_miner_info / _read_miner_limits helpers and a _temp_miner_for_controller builder, reused by the miner- and controller-level reads to avoid duplication.

Frontend

• The "Add Miner" form enables the fetch buttons for Max Hash Rate, Max Power and Model when at least one controller is selected.
• In creation mode the selected controllers are tried until one provides the value; saved miners keep using the miner-level endpoints (which respect feature priority).
• Fetched values populate and highlight the corresponding fields; if no controller provides a value the action fails gracefully with a readable message.

Closes #49

Test plan

• Backend: ruff check / ruff format clean; MinerActionService remains concrete.
• Frontend: vue-tsc -b passes.
• Manual: Add a miner, select a controller that supports detection → fetch Max Hash Rate / Max Power / Model → fields populate and highlight, without saving first.
• Manual: Editing an existing miner still fetches via the miner-level endpoints as before.