数据层可插拔(SQLite/MariaDB) + 后端 services 骨架

- database.ts 改为按 DB_TYPE 切换 SQLite / MariaDB(mysql2)，sqlite3 按需动态导入
- index.ts 改为初始化数据库后再监听端口
- 新增 AuthService / HealthService / AnalysisService / GarminService
- 新增 .gitignore、server/.env(忽略) 与 .env.example
- README 增加数据库配置说明；package.json 增加 mysql2/@types

server/src/index.ts

@@ -20,9 +20,6 @@ app.use(cors({
   credentials: true
 }));
 
-// Initialize database
-initializeDatabase();
-
 // Routes
 app.use('/api/auth', authRoutes);
 app.use('/api/garmin', garminRoutes);
@@ -37,6 +34,14 @@ app.get('/api/health/status', (req, res) => {
 // Error handling
 app.use(errorHandler);
 
-app.listen(PORT, () => {
-  console.log(`Server running on http://localhost:${PORT}`);
-});
+// Initialize database, then start accepting requests
+initializeDatabase()
+  .then(() => {
+    app.listen(PORT, () => {
+      console.log(`Server running on http://localhost:${PORT}`);
+    });
+  })
+  .catch((err) => {
+    console.error('[db] Failed to initialize database:', err);
+    process.exit(1);
+  });