Add bounty signal console pixel art

[JunkingA1]

/claim #80

Summary

Adds an original 128x128 pixel-art PNG under assets/pixel-art/ for issue #80.

What changed:

• Added assets/pixel-art/bounty-signal-console.png
• Added scripts/generate_bounty_signal_console.py so the artwork can be reproduced without external dependencies
• Added demos/bounty-signal-console-demo.mp4 as a short demo artifact

Creative Note

I made a compact bounty signal console because the five status lights map cleanly to the project workflow: scope, proof, review, merge, and payout.

Validation

python3 scripts/generate_bounty_signal_console.py --output /private/tmp/bounty-signal-console-check.png
shasum -a 256 assets/pixel-art/bounty-signal-console.png /private/tmp/bounty-signal-console-check.png
sips -g pixelWidth -g pixelHeight assets/pixel-art/bounty-signal-console.png
file assets/pixel-art/bounty-signal-console.png demos/bounty-signal-console-demo.mp4
git diff --cached --check

Results:

9fcbd3083176d94005ec05ce0a5c0267b6c846bf1c8465e3083a5d23d106cfa4  assets/pixel-art/bounty-signal-console.png
9fcbd3083176d94005ec05ce0a5c0267b6c846bf1c8465e3083a5d23d106cfa4  /private/tmp/bounty-signal-console-check.png

pixelWidth: 128
pixelHeight: 128

assets/pixel-art/bounty-signal-console.png: PNG image data, 128 x 128, 8-bit/color RGBA, non-interlaced
demos/bounty-signal-console-demo.mp4: ISO Media, MP4 v2 [ISO 14496-14]