feat: implement WYSIWYG markdown editor with Go backend and React frontend

- Backend: Go HTTP server with Cobra CLI (--data-dir, --port, --host flags)
- CRUD REST API for markdown files with JSON error responses
- File storage in flat directory structure (flat structure, .md files only)
- Comprehensive logrus logging for all operations
- Static file serving for frontend build (./frontend/dist)
- Frontend: React + TypeScript + Tailwind CSS
- Markdown editor with live GFM preview
- File management: list, create, open, save, delete
- Theme system (Dark, Light, System) with persistence
- Responsive design for desktop and mobile
- Backend tests (storage, API handlers) and frontend tests

frontend/tsconfig.json

@@ -0,0 +1,24 @@
+{
+  "compilerOptions": {
+    "target": "ES2020",
+    "useDefineForClassFields": true,
+    "lib": ["ES2020", "DOM", "DOM.Iterable"],
+    "module": "ESNext",
+    "skipLibCheck": true,
+    "moduleResolution": "bundler",
+    "allowImportingTsExtensions": true,
+    "resolveJsonModule": true,
+    "isolatedModules": true,
+    "noEmit": true,
+    "jsx": "react-jsx",
+    "strict": true,
+    "noUnusedLocals": true,
+    "noUnusedParameters": true,
+    "noFallthroughCasesInSwitch": true,
+    "paths": {
+      "@/*": ["./src/*"]
+    }
+  },
+  "include": ["src"],
+  "references": [{"path": "./tsconfig.node.json"}]
+}