Allow customization of the companion buddy character

Feature Request: Companion/Buddy Customization

Current behavior:
The companion buddy (Siltquack, a duck) is hardcoded and cannot be changed or disabled.

Problem:
At $200/month, users should be able to personalize their experience. The current duck looks like the old Twitter logo, which feels cheap for a premium product.

Requested behavior:
Allow users to choose or customize their companion character via settings.json or a UI option.

Suggested implementation:

• Add a companion.character setting in settings.json (e.g. "companion": "dragon")
• Offer preset characters (dragon, cat, robot, fox, etc.)
• Optionally allow custom emoji as companion icon

This is a small change that would significantly improve the user experience for paying customers. Thank you.