ux: 动作收藏按钮从顶部浮窗移到底部，与加入计划并排 + 图标美化

- detail 顶部 favbtn 浮窗(需避让胶囊、丑)移除，改为底部 addbar 内与 CTA 并排的方形按钮
- fc-icon 新增 filled 属性：收藏态实心心形(Lucide 描边图标默认 fill=none，filled=true 时 fill=stroke 变实心)
- 收藏按钮美化：圆角 24rpx 方形 + 发丝边框，未收藏描边(text-2)、已收藏实心(accent)+ accent-soft 底色 + accent-ring 边框 + 点按 scale 反馈
- detail.js 清理 favRight/favTop 胶囊避让逻辑(不再需要)

miniprogram/pages/detail/detail.js

@@ -7,8 +7,6 @@ const auth = require('../../utils/auth');
 Page({
   data: {
     statusBarHeight: 20,
-    favRight: 8,
-    favTop: 20,
     id: '',
     planId: '',
     exercise: null,
@@ -23,18 +21,7 @@ Page({
   onLoad(query) {
     const id = query.id || '';
     const planId = query.planId || '';
-    // 收藏按钮需避让微信右上角胶囊按钮(···◯)：用胶囊实际位置算出安全右/上边距
-    let favRight = 8;
-    let favTop = (app.globalData.statusBarHeight || 20) + 6;
-    try {
-      const menu = wx.getMenuButtonBoundingClientRect();
-      const win = (wx.getWindowInfo && wx.getWindowInfo()) || wx.getSystemInfoSync();
-      if (menu && win) {
-        favRight = Math.max(8, win.windowWidth - menu.left + 8);
-        favTop = menu.top + Math.max(0, (menu.height - 36) / 2);
-      }
-    } catch (e) {}
-    this.setData({ statusBarHeight: app.globalData.statusBarHeight || 20, favRight, favTop, id, planId });
+    this.setData({ statusBarHeight: app.globalData.statusBarHeight || 20, id, planId });
     // 防御：id 缺失直接显示空态，避免请求 /api/exercises/ 导致错乱或 404
     if (!id) {
       this.setData({ loading: false });