Factory widget: import/export alloy files

[joelteply]

Summary

Factory widget should be able to:

1. Export: Save current forge settings as a .alloy.json recipe
2. Import: Load a .alloy.json to populate forge controls
3. Display: Show executed alloy results (benchmarks, hardware grid, samples) after forge completes
4. Download: Provide download link for the executed alloy from published models

Why

Alloys are the portable format — users should be able to share recipes and results through the UI, not just CLI.

Depends on

• forge-alloy TypeScript package (CambrianTech/forge-alloy)
• model/forge already sends alloys (done: commit 196a9e2)