docs: create roadmap (10 phases)
Phases:
1. Foundation: Database, migrations, repository, deployment
2. Plugin System: Discovery, lifecycle, dependencies, extension API
3. Component System: Reusable UI with HTMX
4. Theme Engine: Layouts, partials, Vue integration
5. CLI Scaffolding: Plugin/theme/component commands
6. Backend Authentication: Users, login, RBAC
7. Admin Forms & Lists: YAML-driven generation
8. Admin Dashboard: Widgets and settings
9. Content Management: Pages, media, menus
10. Core Plugins: User and Blog plugins
All 43 v1 requirements mapped to phases.
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