🚀 Feature: Update favicon/icon/logo assets to the new ones

[JoshuaKGoldberg]

Feature Request Checklist

• I have pulled the latest main branch of the repository.
• I have searched for related issues and found none that matched my issue.

Overview

We have a new, cleaner, logo for 2025 courtesy of Hadley. But the website still uses the old one:

• https://github.com/SquiggleTools/SquiggleConf2025/blob/81915fdcecfaf5f0778d765f76ce82f9a3b38250/public/apple-touch-icon.png
• https://github.com/SquiggleTools/SquiggleConf2025/blob/81915fdcecfaf5f0778d765f76ce82f9a3b38250/public/favicon.ico
• https://github.com/SquiggleTools/SquiggleConf2025/blob/81915fdcecfaf5f0778d765f76ce82f9a3b38250/public/favicon.png
• ...perhaps other places

Time to update to the new one

Additional Info

Assigning to @ceci21 as new in-person website volunteer person.

💖

[JoshuaKGoldberg]

Ceci is out this week so I'll take this on.