Multi-model profile management

[thedavidweng]

Problem

No way to save and switch between different model/backend configurations (e.g., "fast draft" vs "high quality" vs "experimental").

Scope

• Profile data model: name, model variant, inference steps, guidance scale, and other generation defaults
• CRUD operations for profiles (create, rename, apply, delete)
• Settings UI section for profile management
• CLI openloop profiles subcommand group
• Generation history records which profile was used

Acceptance criteria

• Users can create named profiles with different generation defaults
• Switching a profile updates the form fields
• History shows which profile was used for each generation
• CLI supports openloop profiles list, openloop profiles create, openloop profiles delete