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/scripts/dev.sh

@@ -0,0 +1,20 @@
+#!/bin/sh
+set -eu
+
+backend_dir=$(CDPATH= cd -- "$(dirname -- "$0")/.." && pwd)
+cd "$backend_dir"
+
+if [ ! -f .env ]; then
+  printf '%s\n' '缺少 backend/.env，请先从 .env.example 复制并配置。' >&2
+  exit 1
+fi
+
+# Only source trusted local configuration; .env uses shell assignment syntax.
+set -a
+. ./.env
+set +a
+
+go build -o bin/api ./cmd/server
+# Replace the shell so shutdown signals reach the Go process directly.
+exec ./bin/api
+