Release v1.9.2: Full-width background for code blocks

Fixed code block and ASCII art background to extend full paragraph width:

🔧 Background Fix:
- Moved shading (w:shd) from run level (<w:rPr>) to paragraph level (<w:pPr>)
- Background now extends full width like in the preview
- Applied to both createCodeBlockXml() and createAsciiArtXml() functions

📝 Technical Changes:
- src/wordTemplateExporter.js: Paragraph-level shading for full-width backgrounds
- Added w:ind with left="284" right="284" for consistent margins
- Removed redundant w:shd from run properties

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

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

CLAUDE.md

@@ -4,7 +4,7 @@
 
 **PanConverter** is a cross-platform Markdown editor and converter powered by Pandoc, built with Electron. It provides professional-grade editing capabilities with comprehensive export options.
 
-**Current Version**: v1.9.1
+**Current Version**: v1.9.2
 **Author**: Amit Haridas (amit.wh@gmail.com)
 **License**: MIT
 **Repository**: https://github.com/amitwh/pan-converter