brand: add PNG renders of the logo

public/logo/icon-{32,180,512,1024}.png — square, centered,
transparent. Use:
  - 32       favicon fallback
  - 180      Apple touch icon
  - 512      PWA manifest
  - 1024     general high-res

Plus icon-wide-256.png — preserves the original 112:91 aspect,
useful for inline header use.

Rendered from app/icon.svg via rsvg/magick at high density so
strokes stay crisp at any reasonable display size.

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

Author: khaliqgant