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/pages/collection-detail/collection-detail.wxml

@@ -0,0 +1,24 @@
+<view class="page" wx:if="{{collection}}">
+  <navbar title="{{collection.name}}" show-back />
+
+  <view class="header" style="background: linear-gradient(135deg, {{collection.color}}26, var(--surface));">
+    <view class="header__emoji" style="background: {{collection.color}}22; color: {{collection.color}};">{{collection.emoji}}</view>
+    <view class="header__name">{{collection.name}}</view>
+    <view class="header__desc">{{collection.description}}</view>
+    <view class="header__count" style="color: {{collection.color}};">共 {{total}} 个动作</view>
+  </view>
+
+  <view class="section" style="padding-top: 8rpx;">
+    <view class="grid" wx:if="{{exercises.length}}">
+      <view class="grid__item" wx:for="{{exercises}}" wx:key="id">
+        <exercise-card exercise="{{item}}" bind:tap="onExercise" />
+      </view>
+    </view>
+    <view wx:elif="{{!loading}}" class="empty">暂无数据</view>
+    <view wx:else class="empty">加载中…</view>
+  </view>
+</view>
+
+<view wx:else class="empty-page">
+  <view class="empty">{{ loading ? '加载中…' : '未找到该训练组合' }}</view>
+</view>