refactor: move all styles to public/assets/css

- Remove duplicate CSS files from src/assets
- Keep all stylesheets in public/assets/css for static serving
- Update style.css imports to reference public assets
- Cleaner separation: public for styles, src for Vue components

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

src/style.css

@@ -1,2 +1,2 @@
-@import url('./assets/pagedjs-interface.css');
-@import url('./assets/editor-ui.css');
+@import url('/assets/css/pagedjs-interface.css');
+@import url('/assets/css/editor-ui.css');