feat: Add Markdown to PDF conversion functionality (#59)

* feat: Add Markdown to PDF conversion functionality

- Implement dual-panel interface with live preview
- Support 3 Markdown flavors: GitHub, CommonMark, Pandoc
- Add file upload support for .md files
- Implement image quality settings (High/Medium/Low)
- Add professional user messaging and error handling
- Support all common Markdown elements (headers, lists, tables, code blocks, etc.)
- Add automatic navigation back to tool after completion

Resolves #37

* fix: improve markdown to PDF conversion with math support and better rendering

- Add KaTeX support for mathematical expressions (inline and block math)
- Fix horizontal separator rendering with improved CSS
- Enhance table rendering with proper borders and cell styling
- Replace CDN dependencies with local KaTeX installation
- Add comprehensive math preprocessing for $...$ and 20112...20112 syntax
- Improve markdown preview with real-time math rendering
- Update UI placeholder text with math examples
- Add fallback rendering for math expressions when KaTeX fails

Resolves issues with:
- Horizontal separators not rendering properly
- Tables missing borders and proper structure
- Mathematical expressions not displaying correctly

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Co-authored-by: syazkun <mohamadsyazwan193@gmail.com>

package.json

@@ -48,7 +48,9 @@
     "javascript-obfuscator": "^4.1.1",
     "jspdf": "^3.0.3",
     "jszip": "^3.10.1",
-    "lucide": "^0.546.0",
+    "katex": "^0.16.25",
+    "lucide": "^0.545.0",
+    "marked": "^16.4.1",
     "pdf-lib": "^1.17.1",
     "pdfjs-dist": "^5.4.296",
     "pdfkit": "^0.17.2",