Add verification dry dock pixel art

[vultuk]

Summary

• Add original 128x128 PNG pixel art at assets/pixel-art/verification-dry-dock.png.
• Add a deterministic stdlib generator at assets/pixel-art/generate_verification_dry_dock.py so reviewers can reproduce the asset.
• Add a short demo video at demos/verification-dry-dock-demo.ogv.

/claim #80

Creative note: I made a verification dry dock where scoped work moves past proof buoys, review lights, and a payout crane, because it fits the bounty workflow while staying distinct from the recent orbit station, review altar, greenhouse, elevator, train, switchboard, kiln, and loom submissions.

Validation

• python3 assets/pixel-art/generate_verification_dry_dock.py
• file assets/pixel-art/verification-dry-dock.png -> 128 x 128 RGBA PNG
• PNG header parsed locally as 128x128
• Reproduced PNG SHA-256: 88f5fc00f82f03c8076dcab0e040fbe133d01498a3d22bf08901b35ed871a85c
• file demos/verification-dry-dock-demo.ogv -> Ogg data, Theora video
• python3 -m py_compile assets/pixel-art/generate_verification_dry_dock.py
• git diff --check --cached before commit

[vultuk]

Payment note: if the sponsor supports direct crypto/BTC payout for this bounty, please use BTC address bc1qa5acxqc3wldzxwjhe8a65gjp6n7dxmafm6qs4j. Otherwise I will follow the platform payout flow.