Initial commit: WYSIWYG Markdown Editor - Go backend + React/TypeScript frontend with Tailwind CSS

Backend:
- Cobra CLI with --data-dir, --port, --host flags
- Gin HTTP server with REST API for markdown CRUD operations
- File storage on disk (.md files only)
- Comprehensive logrus logging
- Backend tests with CRUD round-trip verification

Frontend:
- React 18 + TypeScript + Tailwind CSS
- Markdown editor with live GFM preview (react-markdown + remark-gfm)
- File management UI (list, create, open, save, delete)
- Theme switcher with Dark/Light/System modes
- Responsive design
- Frontend tests with vitest

Testing:
- All backend tests pass (go test ./...)
- All frontend tests pass (npm test)

frontend/tsconfig.node.json

@@ -0,0 +1,10 @@
+{
+  "compilerOptions": {
+    "composite": true,
+    "skipLibCheck": true,
+    "module": "ESNext",
+    "moduleResolution": "bundler",
+    "allowSyntheticDefaultImports": true
+  },
+  "include": ["vite.config.ts"]
+}