feat(report-viewer): add syntax highlighting and GitHub-style markdown rendering

Add rehype plugins for enhanced markdown rendering:
- rehype-highlight: syntax highlighting for code blocks
- rehype-slug: generates heading IDs for anchoring
- rehype-autolink-headings: auto-links headings
- github-markdown-css: GitHub-flavored markdown styling

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

package.json

@@ -39,6 +39,7 @@
     "chromium-bidi": "^15.0.0",
     "date-fns": "^4.1.0",
     "exceljs": "^4.4.0",
+    "github-markdown-css": "^5.9.0",
     "js-yaml": "^4.1.1",
     "lucide-react": "^0.575.0",
     "mssql": "^12.2.0",
@@ -48,6 +49,9 @@
     "react-focus-lock": "^2.13.7",
     "react-markdown": "^10.1.0",
     "reflect-metadata": "^0.2.2",
+    "rehype-autolink-headings": "^7.1.0",
+    "rehype-highlight": "^7.0.2",
+    "rehype-slug": "^6.0.0",
     "remark-gfm": "^4.0.1",
     "typeorm": "^0.3.28",
     "uuid": "^13.0.0",