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/compose.yaml

@@ -0,0 +1,49 @@
+name: ballet-island
+
+services:
+  postgres:
+    image: postgres:18-alpine
+    restart: unless-stopped
+    environment:
+      POSTGRES_DB: ${PGDATABASE:?Set PGDATABASE in .env}
+      POSTGRES_USER: ${PGUSER:?Set PGUSER in .env}
+      POSTGRES_PASSWORD: ${PGPASSWORD:?Set PGPASSWORD in .env}
+    ports:
+      - "127.0.0.1:${PGPORT:-5432}:5432"
+    volumes:
+      # PostgreSQL 18 stores its versioned data directory under this mount.
+      - postgres_data:/var/lib/postgresql
+    healthcheck:
+      test: ["CMD-SHELL", "pg_isready -U \"$$POSTGRES_USER\" -d \"$$POSTGRES_DB\""]
+      interval: 5s
+      timeout: 3s
+      retries: 10
+      start_period: 10s
+
+  api:
+    build:
+      context: .
+    restart: unless-stopped
+    environment:
+      HTTP_ADDR: :8080
+      PGHOST: postgres
+      PGPORT: 5432
+      PGDATABASE: ${PGDATABASE:?Set PGDATABASE in .env}
+      PGUSER: ${PGUSER:?Set PGUSER in .env}
+      PGPASSWORD: ${PGPASSWORD:?Set PGPASSWORD in .env}
+      PGSSLMODE: disable
+    ports:
+      - "${API_BIND:-127.0.0.1}:${API_PORT:-8080}:8080"
+    depends_on:
+      postgres:
+        condition: service_healthy
+    healthcheck:
+      test: ["CMD", "wget", "-q", "-T", "3", "-O", "/dev/null", "http://127.0.0.1:8080/readyz"]
+      interval: 10s
+      timeout: 5s
+      retries: 3
+      start_period: 10s
+    stop_grace_period: 15s
+
+volumes:
+  postgres_data: