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.js

@@ -0,0 +1,20 @@
+Component({
+  properties: {
+    active: { type: String, value: 'home' } // 'home' | 'category' | 'plan'
+  },
+  data: {
+    items: [
+      { key: 'home', label: '首页', emoji: '🏠', page: '/pages/index/index' },
+      { key: 'category', label: '分类', emoji: '📚', page: '/pages/category/category' },
+      { key: 'plan', label: '计划', emoji: '📋', page: '/pages/collection/collection' }
+    ]
+  },
+  methods: {
+    onTap(e) {
+      const page = e.currentTarget.dataset.page;
+      if (!page) return;
+      // 使用 reLaunch 重置页面栈，避免页面层级堆叠
+      wx.reLaunch({ url: page });
+    }
+  }
+});

miniprogram/components/bottom-nav/index.json

@@ -0,0 +1,4 @@
+{
+  "component": true,
+  "usingComponents": {}
+}

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>

miniprogram/components/bottom-nav/index.wxss

@@ -0,0 +1,22 @@
+.bn {
+  position: fixed;
+  left: 0; right: 0; bottom: 0;
+  display: flex;
+  background: rgba(20,26,22,0.92);
+  backdrop-filter: blur(12px);
+  border-top: 1rpx solid var(--line);
+  padding-bottom: env(safe-area-inset-bottom);
+  z-index: 60;
+}
+.bn__item {
+  flex: 1;
+  display: flex;
+  flex-direction: column;
+  align-items: center;
+  padding: 16rpx 0 14rpx;
+  color: var(--text-3);
+}
+.bn__item--active { color: var(--gold); }
+.bn__emoji { font-size: 40rpx; line-height: 1; }
+.bn__label { font-size: 22rpx; margin-top: 6rpx; }
+.bn__item--active .bn__label { color: var(--gold-2); }