[Docs] Create a "UNA vs. LLC" Comparison Guide

[mijinummi]

Title: [Docs] Create a "UNA vs. LLC" Decision-Making Guide for Devs

📝 Description

New collectives often don't know which legal "wrapper" to choose. We need a side-by-side comparison to help them decide if a UNA is right for them.

🎯 Goal

Write a guide in docs/guides/una-vs-llc.md.

✅ Requirements

• Compare on: Cost to Form, Privacy/Anonymity, Complexity, and Liability Protection.
• Highlight the "Non-Profit" nature of a UNA (e.g., it's for building protocols, not necessarily for distributing dividends like a corp).
• Use a clear Markdown table for the comparison.