Major changes:
- Custom .tpl template engine (Lexer, Parser, Interpreter)
- Widget system: declarative JSON + .tpl, no PHP in widgets
- WidgetDataService: whitelisted Model.method provider registry
- All 8 themes converted from PHP to .tpl with full i18n
- Asset pipeline: file copies replace symlinks
- Theme validation: PHP detection blocks malicious themes
- Admin forms auto-generated from widget_info.json
- Premium gating on author bio
- Page-level output caching with configurable TTL