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)

cmd/main_test.go

@@ -0,0 +1,26 @@
+package main
+
+import (
+	"testing"
+)
+
+func TestExecute(t *testing.T) {
+	// Just verify the command structure
+	cmd := rootCmd
+	if cmd == nil {
+		t.Error("rootCmd is nil")
+	}
+	if cmd.Use != "markdown-editor" {
+		t.Errorf("Expected Use 'markdown-editor', got '%s'", cmd.Use)
+	}
+}
+
+func TestRunServer(t *testing.T) {
+	cmd := rootCmd
+	if cmd == nil {
+		t.Error("rootCmd is nil")
+	}
+	if cmd.Use != "markdown-editor" {
+		t.Errorf("Expected Use 'markdown-editor', got '%s'", cmd.Use)
+	}
+}