Refresh README visuals to match earlyon and trtcheck

[sohams25]

• Banner, result summary and architecture rebuilt in the shared visual language of the sibling repositories: GitHub-dark card canvas, large monospace title, hairline rules, one concept per graphic, semantic green/red accents (dark mode only).
• Architecture diagram now uses clean orthogonal bus routing and shows the measured path only.
• Matplotlib charts restyled to the same dark canvas and palette; regenerated from committed data.
• Camera section condensed to describe the input path used; full details remain in docs/limitations.md.
• No benchmark data, runtime code, tag or release changes; all numbers unchanged and re-verified; tests, links and SVG validation pass.