Add comprehensive technical specification for Movie Creator Web App

- Detailed architecture including Next.js 14+ with App Router
- Complete data models for projects, timeline, assets, and render jobs
- Zustand state management structure with persistence strategy
- Remotion integration architecture and rendering pipeline
- Component breakdown for editor, timeline, and canvas
- Performance optimization strategies for large files and timeline
- Feature roadmap from MVP to advanced AI-powered features
- Testing, deployment, and security considerations

Author: claude