Initial commit: Set up Garmin Health Lab project structure

- Initialize monorepo with root workspace configuration
- Set up Express.js backend with TypeScript
- Set up React 18 frontend with TypeScript
- Create database schema with SQLite
- Implement project architecture and documentation
- Add development and deployment guidelines

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

client/src/pages/DataSync.tsx

@@ -0,0 +1,20 @@
+import React from 'react';
+import './Pages.css';
+
+function DataSync() {
+  const handleSync = async () => {
+    // TODO: Implement data sync
+  };
+
+  return (
+    <div className="page">
+      <h2>数据同步</h2>
+      <p className="placeholder">数据同步功能即将推出...</p>
+      <button onClick={handleSync} className="btn btn-primary">
+        同步 Garmin 数据
+      </button>
+    </div>
+  );
+}
+
+export default DataSync;