Redesign README with badges, tables, collapsible sections, and visual layout

Visual overhaul for better GitHub presentation:
- Shield badges at top (platform, safety, tests, license)
- Centered title and tagline
- Collapsible demo section
- Two-column safety model table
- Cleaner feature cards with blockquotes
- Consistent table formatting throughout
- Contributing section as a table
- Centered footer

Author: rish-e