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

miniprogram/components/bottom-nav/index.wxml

@@ -0,0 +1,11 @@
+<view class="bn">
+  <view
+    wx:for="{{items}}"
+    wx:key="key"
+    class="bn__item {{active === item.key ? 'bn__item--active' : ''}}"
+    data-page="{{item.page}}"
+    bindtap="onTap">
+    <text class="bn__emoji">{{item.emoji}}</text>
+    <text class="bn__label">{{item.label}}</text>
+  </view>
+</view>