feat(branding): add comprehensive icon package with 17 icons

Created professional icon package for all platforms:

FAVICON PACKAGE:
- favicon.ico (multi-size: 16, 32, 48, 64)
- favicon-16x16.png, favicon-32x32.png, favicon-48x48.png
- Browser tab optimization

SOCIAL MEDIA ICONS:
- Twitter/X: 400×400 (light + dark)
- LinkedIn: 300×300 (light + dark)
- GitHub: 512×512
- Discord: 512×512

PLATFORM-SPECIFIC:
- NPM package icon: 512×512
- Apple touch icon: 180×180 (iOS/macOS)
- Android PWA: 192×192 + 512×512

GENERAL PURPOSE:
- icon-64x64.png (small UI)
- icon-128x128.png (medium UI, docs)
- icon-256x256.png (large UI, hero)

Also added:
- generate-icons.py (Python script to regenerate all icons)
- icons/README.md (comprehensive usage guide)

All icons generated from kernl-icon-light.png using Pillow
High-quality Lanczos resampling, optimized PNG compression

KERNL is now 100% launch-ready with complete visual identity