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/category/category.wxml

@@ -0,0 +1,29 @@
+<view class="page">
+  <navbar title="{{title}}" show-back />
+
+  <view class="section" style="padding-top: 8rpx;">
+    <scroll-view wx:if="{{values.length}}" scroll-x class="filterbar">
+      <chip
+        wx:for="{{values}}"
+        wx:key="value"
+        label="{{item.label}}"
+        value="{{item.value}}"
+        active="{{activeValue === item.value}}"
+        bind:tap="onValue" />
+      <view class="filterbar__spacer"></view>
+    </scroll-view>
+
+    <view class="count muted" wx:if="{{!loading}}">共 {{total}} 个动作</view>
+
+    <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 style="height: 160rpx;"></view>
+  <bottom-nav active="category" />
+</view>