feat: support multi-page editing and printing #1
Description
Summary
- add multi-page editing with per-page markdown editors and previews
- fix browser printing so each preview page prints as its own A4 page
- update README usage instructions for multi-page workflow and printing
Motivation
The app currently focuses on fitting content into a single printable page. This feature expands the workflow to support multiple independently edited pages while keeping the preview and print output aligned.
Scope
- add page management in the editor UI
- render multiple A4 preview pages
- ensure print mode removes preview-only layout constraints
- document the updated usage flow in README
Acceptance Criteria
- users can add and remove pages in the editor UI
- each page has its own preview and fit calculation
- print preview shows all pages instead of only the first page
- printed pages are aligned correctly without right offset
- README explains basic usage, multi-page editing, and printing