feat: initialize Ballet Island 微信小程序 with basic structure and functionality

- Add project configuration for WeChat mini program.
- Create skills lock file for Taroify integration.
- Set up app configuration and styles.
- Implement main app component and index page with welcome message.
- Add health check service to verify backend readiness.
- Configure TypeScript settings and global types.

backend/go.mod

@@ -0,0 +1,13 @@
+module ballet-island/backend
+
+go 1.26.0
+
+require github.com/jackc/pgx/v5 v5.11.0
+
+require (
+	github.com/jackc/pgpassfile v1.0.0 // indirect
+	github.com/jackc/pgservicefile v0.0.0-20240606120523-5a60cdf6a761 // indirect
+	github.com/jackc/puddle/v2 v2.2.2 // indirect
+	golang.org/x/sync v0.17.0 // indirect
+	golang.org/x/text v0.29.0 // indirect
+)