Show friendly model names for discovered devices

[jfmlima]

Purpose

Show friendly Shelly model names (Shelly Plus 2PM) instead of raw SKUs (SNSW-102P16EU) in the dashboard table, the device detail page, and CLI tables.

Context

Closes #78. The model to marketing name mapping is vendored from aioshelly's table (150 models, Gen1 through Gen4). Unknown models fall back to the raw model ID, so new hardware renders exactly as before. The Model column filters and sorts on both the friendly name and the raw ID since both are visible.

Notes

• model_name is a computed field on DiscoveredDevice, so the scan response and CLI pick it up without per-call wiring.
• The device detail summary previously carried no model info at all; it now includes device_type and model_name.
• The Columns dropdown now shows the translated column labels instead of raw ids.
• Deliberately not done: renaming Device Name to Hostname (that column shows the name set on the device, not the hostname) and any auto sync for the mapping (unmapped models degrade to today's behavior, entries get added on report).
• Pre-existing gaps left as is: the scan route returns untyped dicts so DeviceResponse stays dead code, the CLI README device status example doesn't match the real detail panel output, and it documents a scan --export flag that doesn't exist.