feat: init fitness-coach (backend + miniprogram)

- backend: NestJS service with exercise/plan data
- miniprogram: WeChat mini program client
- exclude node_modules, dist, runtime data-store, local env

backend/scripts/copy-data.mjs

@@ -0,0 +1,20 @@
+// 将原始数据集 exercises.json 从 src 复制到编译产物 dist，
+// 因为 tsc 不会拷贝非 .ts 资源文件。
+import * as fs from 'fs';
+import * as path from 'path';
+import { fileURLToPath } from 'url';
+
+const __dirname = path.dirname(fileURLToPath(import.meta.url));
+const root = path.resolve(__dirname, '..');
+const src = path.join(root, 'src', 'exercises', 'data', 'exercises.json');
+const destDir = path.join(root, 'dist', 'exercises', 'data');
+const dest = path.join(destDir, 'exercises.json');
+
+if (!fs.existsSync(src)) {
+  console.warn('[copy-data] 源数据集不存在，跳过:', src);
+  process.exit(0);
+}
+
+fs.mkdirSync(destDir, { recursive: true });
+fs.copyFileSync(src, dest);
+console.log('[copy-data] 已复制数据集 ->', dest);