Add seed script with 7 trees, markdown rendering, and dark mode docs

- Add comprehensive seed script with 7 troubleshooting decision trees
  - Tier 1: Password Reset, Outlook/Email, VPN, Printer Problems
  - Tier 2: Slow Computer, Network Connectivity
  - Tier 3: File Share Access Problems
- Add markdown rendering with react-markdown package
  - MarkdownContent component for session player and node editor
  - Preview toggle in description fields
- Update documentation to reflect dark mode is complete
- Update all progress tracking docs with recent changes

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

frontend/package.json

@@ -17,6 +17,7 @@
     "lucide-react": "^0.563.0",
     "react": "^19.2.0",
     "react-dom": "^19.2.0",
+    "react-markdown": "^10.1.0",
     "react-router-dom": "^7.13.0",
     "tailwind-merge": "^3.4.0",
     "zundo": "^2.3.0",