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/section-header/index.wxml

@@ -0,0 +1,8 @@
+<view class="sh">
+  <view class="sh__main">
+    <view wx:if="{{eyebrow}}" class="eyebrow">{{eyebrow}}</view>
+    <view class="sh__title">{{title}}</view>
+    <view wx:if="{{subtitle}}" class="sh__sub">{{subtitle}}</view>
+  </view>
+  <view wx:if="{{action}}" class="sh__action" bindtap="onAction">{{action}} ›</view>
+</view>