fix: revert to 4KB icon CSS-upscaled to 160px + text branding

Two large base64 images (33KB) caused 4.8s render — Twitter timeout.
Back to single 4KB icon upscaled via CSS width/height to 160px.
"Fast Protocol" and "fastprotocol.io" rendered as text (no image load).

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: techgangboss