Override mermaid's default white backgrounds to blend with dark theme:
- Transparent SVG background
- Node fills use --bg-sidebar
- Labels use --fg color
- Edges use --fg-muted
- Add sidebar footer with GitHub repo link and MIT copyright
- Generate geometric logo for project branding
- Add logo as favicon in browser tab
- Add logo to sidebar header (32x32) next to "sukr" text
- Add centered logo (128px) at top of README