docs: consolidate documentation into comprehensive guide

- Remove old documentation files (QUICK_REFERENCE.md, README.md, SF_WEBAPP_DEV_DOCUMENTATION.md)
- Add SF_WEBAPP_DEV_GUIDE.md - comprehensive guide covering:
  - Overview and architecture
  - Getting started and building
  - Command usage and options
  - File structure and components
  - VSCode integration details
  - Advanced features (hot reload, error capture, etc.)
  - Troubleshooting and FAQ

Single source of truth for all webapp dev command documentation.

Author: deepu-mungamuri94