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

---------

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

package-lock.json

@@ -18,7 +18,9 @@
         "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",
@@ -8269,6 +8271,31 @@
         "setimmediate": "^1.0.5"
       }
     },
+    "node_modules/katex": {
+      "version": "0.16.25",
+      "resolved": "https://registry.npmjs.org/katex/-/katex-0.16.25.tgz",
+      "integrity": "sha512-woHRUZ/iF23GBP1dkDQMh1QBad9dmr8/PAwNA54VrSOVYgI12MAcE14TqnDdQOdzyEonGzMepYnqBMYdsoAr8Q==",
+      "funding": [
+        "https://opencollective.com/katex",
+        "https://github.com/sponsors/katex"
+      ],
+      "license": "MIT",
+      "dependencies": {
+        "commander": "^8.3.0"
+      },
+      "bin": {
+        "katex": "cli.js"
+      }
+    },
+    "node_modules/katex/node_modules/commander": {
+      "version": "8.3.0",
+      "resolved": "https://registry.npmjs.org/commander/-/commander-8.3.0.tgz",
+      "integrity": "sha512-OkTL9umf+He2DZkUq8f8J9of7yL6RJKI24dVITBmNfZBmri9zYZQrKkuXiKhyfPSu8tUhnVBB1iKXevvnlR4Ww==",
+      "license": "MIT",
+      "engines": {
+        "node": ">= 12"
+      }
+    },
     "node_modules/keyv": {
       "version": "4.5.4",
       "resolved": "https://registry.npmjs.org/keyv/-/keyv-4.5.4.tgz",
@@ -8746,6 +8773,18 @@
         "node": ">=0.10.0"
       }
     },
+    "node_modules/marked": {
+      "version": "16.4.1",
+      "resolved": "https://registry.npmjs.org/marked/-/marked-16.4.1.tgz",
+      "integrity": "sha512-ntROs7RaN3EvWfy3EZi14H4YxmT6A5YvywfhO+0pm+cH/dnSQRmdAmoFIc3B9aiwTehyk7pESH4ofyBY+V5hZg==",
+      "license": "MIT",
+      "bin": {
+        "marked": "bin/marked.js"
+      },
+      "engines": {
+        "node": ">= 20"
+      }
+    },
     "node_modules/math-intrinsics": {
       "version": "1.1.0",
       "resolved": "https://registry.npmjs.org/math-intrinsics/-/math-intrinsics-1.1.0.tgz",