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/sync-media.mjs

@@ -0,0 +1,74 @@
+/**
+ * 媒体同步脚本：将 exercises-dataset 的 images/ 与 videos/ 下载到 backend/media/，
+ * 使后端 /media 静态服务可直接提供缩略图与动画 GIF。
+ *
+ * 用法： node scripts/sync-media.mjs
+ * 可选环境变量：
+ *   MEDIA_CONCURRENCY=8   并发下载数
+ *   MEDIA_ONLY=gif|image  仅下载某类（gif / image）
+ */
+import * as fs from 'fs';
+import * as path from 'path';
+import { fileURLToPath } from 'url';
+
+const __dirname = path.dirname(fileURLToPath(import.meta.url));
+const DATA_FILE = path.join(__dirname, '..', 'src', 'exercises', 'data', 'exercises.json');
+const MEDIA_DIR = path.join(__dirname, '..', 'media');
+const RAW_BASE = 'https://raw.githubusercontent.com/hasaneyldrm/exercises-dataset/main/';
+const CONCURRENCY = parseInt(process.env.MEDIA_CONCURRENCY || '8', 10);
+const ONLY = process.env.MEDIA_ONLY || 'all';
+
+async function main() {
+  if (!fs.existsSync(DATA_FILE)) {
+    console.error('[sync-media] 未找到数据集，请先运行 npm run build 或手动放置 exercises.json');
+    process.exit(1);
+  }
+  const raw = JSON.parse(fs.readFileSync(DATA_FILE, 'utf-8'));
+  const paths = new Set();
+  for (const e of raw) {
+    if (e.image && (ONLY === 'all' || ONLY === 'image')) paths.add(e.image);
+    if (e.gif_url && (ONLY === 'all' || ONLY === 'gif')) paths.add(e.gif_url);
+  }
+
+  fs.mkdirSync(MEDIA_DIR, { recursive: true });
+  const list = Array.from(paths);
+  console.log(`[sync-media] 待下载媒体 ${list.length} 个，并发 ${CONCURRENCY}`);
+
+  let done = 0;
+  let skipped = 0;
+  let failed = 0;
+  const queue = [...list];
+
+  async function worker() {
+    while (queue.length) {
+      const p = queue.shift();
+      const dest = path.join(MEDIA_DIR, p);
+      if (fs.existsSync(dest) && fs.statSync(dest).size > 0) {
+        skipped++;
+        continue;
+      }
+      try {
+        const res = await fetch(RAW_BASE + p);
+        if (!res.ok) throw new Error(`HTTP ${res.status}`);
+        const buf = Buffer.from(await res.arrayBuffer());
+        fs.mkdirSync(path.dirname(dest), { recursive: true });
+        fs.writeFileSync(dest, buf);
+        done++;
+      } catch (err) {
+        failed++;
+        console.error(`  失败 ${p}: ${err.message}`);
+      }
+      if ((done + skipped + failed) % 50 === 0) {
+        console.log(`  进度 ${done + skipped + failed}/${list.length}`);
+      }
+    }
+  }
+
+  await Promise.all(Array.from({ length: CONCURRENCY }, () => worker()));
+  console.log(`[sync-media] 完成：新增 ${done}，已存在 ${skipped}，失败 ${failed}`);
+}
+
+main().catch((e) => {
+  console.error('[sync-media] 错误:', e.message);
+  process.exit(1);
+});