fix(public): add apple-touch-icon + precomposed variant

Eliminates 16 404s/week on docs from iOS clients requesting
/apple-touch-icon.png and /apple-touch-icon-precomposed.png.
180×180 PNG matching sharpapi-site branding.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: Mlaz-code