docs: add ETHGlobal submission images (logo, cover, 6 screenshots)

- logo-512x512.png: dark/lime SimoProof SP monogram logo
- cover-1280x720.png: 16:9 branded cover with pipeline strip, stats, tech badges
- screenshot-01-hero: simoproof.org hero section
- screenshot-02-senate-vote: Bayesian Reasoner ENDORSE live
- screenshot-03-zk-proof: RISC Zero ZK proof in progress
- screenshot-04-pipeline-complete: all 7 steps complete with EAS UID
- screenshot-05-ens-records: ENSIP-25 ENS text records live on Sepolia
- screenshot-06-eas-attestation: decoded EAS attestation on Base Sepolia

Author: web3guru888