Add flash walkthrough video

[weishen612]

Summary

• add a lightweight "Watch walkthrough" entry on the flash.comma.ai page
• embed a 72 second 1080p MP4 walkthrough with a poster image
• keep the existing flashing flow unchanged while making the walkthrough available in a modal video player

Closes #128

Notes

The video uses the existing flash.comma.ai visual language and repository assets, plus self-made animation and procedural audio. It avoids showing a fake completed flash; the walkthrough stops short of claiming a real device was flashed.

Video asset:

• public/flash-walkthrough.mp4
• 1920x1080, H.264/AAC
• 72 seconds
• 2.5 MB

Testing

• npx --yes bun install
• npx --yes bun run test src/app/App.test.jsx --run
• npx --yes bun run build
• Playwright desktop/mobile modal checks

Known unrelated baseline note:

• npx --yes bun run test --run currently fails in src/utils/manifest.test.js because the remote manifest returns 32 images while the test expects 33. The app-focused walkthrough test passes.

[weishen612]

Closing this draft because I’m not continuing it without a real-device walkthrough. The current implementation does not fully match the issue’s intended deliverable, so I do not want to keep this open as a bounty submission.