Add Stack-chan Zoo

[meganetaaan]

Summary

Add:

• Stack-chan Zoo - Collection of Stack-chan-related works on Protopedia.

Category: Community

Source: extracted from the Stack-chan Cosense crawl and checked for public access before PR creation.

Checklist

• I searched existing entries and confirmed this is not a duplicate.
• I added the item to the appropriate category.
• The link is publicly accessible.
• The description is concise and neutral.
• The entry follows the format: - [Name](URL) - Description.
• This is not my own project.