Refactor ObjectQL homepage with compiler-focused content

- Replace protocol specification landing page with homepage content
- Add Hero section emphasizing "Universal Data Compiler" positioning
- Add Show Code section with Schema vs Compiled SQL comparison
- Add Why ObjectQL 3 Pillars: Zero-Overhead Security, Database Agnostic, Virtual Columns
- Add Compiler vs ORM comparison table
- Add Supported Drivers section with technical edge descriptions
- Maintain technical, code-forward tone without marketing fluff
- Keep design philosophy and quick start sections

Co-authored-by: huangyiirene <7665279+huangyiirene@users.noreply.github.com>

Author: Copilot