Features & fixes

### Features

- Featured posts.
- Nested menus.
- New `/edit` route for pages and posts.

### Enhancements

- Restructured metadata page.
- Masked database password field in installer.
- Prevented users from removing themselves (_leading to system lockout_).
- Included all languages.
- SEO keywords.

### Issues

- Fixed page icons not being centered relative to their container.