refactor(ui): 12-point UI polish and bugfixes

Bug fixes:
- #1 Remove duplicate month label from calendar-heatmap (shown twice in records)
- #2 Extract shared .modal-overlay to app.wxss (was duplicated in index/records)

UX improvements:
- #3 Add long-press hint to history list in records page
- #4 Add drag handle + catchtouchmove to picker modal
- #5 Extend timer auto-navigate-back from 1.5s to 3s
- #6 Add clear data option in settings with confirmation dialog

Visual/code polish:
- #7 Remove 4 unused @keyframes (shimmer, spin) and 5 unused .icon classes
- #8 Tab bar inactive colors: hardcoded #888/#666 -> var(--text-secondary)
- #10 Split progress-ring observer to avoid redundant setData on size/color changes
- #12 Remove meaningless Math.min(planDay, 99) cap

pages/index/index.wxml

@@ -79,8 +79,9 @@
 </view>
 
 <!-- 时间选择弹窗 -->
-<view class="modal-overlay" wx:if="{{showPicker}}" bindtap="onClosePicker">
-  <view class="picker-modal" catchtap="noop">
+<view class="modal-overlay modal-overlay-bottom" wx:if="{{showPicker}}" bindtap="onClosePicker">
+  <view class="picker-modal" catchtap="noop" catchtouchmove="noop">
+    <view class="picker-handle"></view>
     <text class="picker-title">⏱ 选择训练时长</text>
     <view class="preset-grid">
       <view

pages/index/index.wxss

@@ -295,28 +295,23 @@
 }
 
 /* ---- picker modal ---- */
-.modal-overlay {
-  position: fixed;
-  top: 0;
-  left: 0;
-  right: 0;
-  bottom: 0;
-  background: rgba(0, 0, 0, 0.45);
-  z-index: 1000;
-  display: flex;
-  align-items: flex-end;
-  justify-content: center;
-}
-
 .picker-modal {
   width: 100%;
   background: #fff;
   border-radius: 32rpx 32rpx 0 0;
-  padding: 40rpx 32rpx;
+  padding: 28rpx 32rpx 40rpx;
   padding-bottom: calc(40rpx + env(safe-area-inset-bottom));
   animation: slideUp 0.3s cubic-bezier(0.32, 0.72, 0, 1);
 }
 
+.picker-handle {
+  width: 64rpx;
+  height: 8rpx;
+  background: #DDD;
+  border-radius: 4rpx;
+  margin: 0 auto 24rpx;
+}
+
 @keyframes slideUp {
   from { transform: translateY(100%); }
   to { transform: translateY(0); }

pages/records/records.wxml

@@ -40,6 +40,7 @@
   <view class="history-section card">
     <view class="history-header">
       <text class="section-title">📋 最近记录</text>
+      <text class="history-hint" wx:if="{{historyList.length > 0}}">长按可删除</text>
     </view>
     <view wx:if="{{historyList.length === 0}}" class="empty-state">
       <text class="empty-emoji">🏃</text>
@@ -63,7 +64,7 @@
   </view>
 
   <!-- 日期详情弹窗 -->
-  <view class="modal-overlay" wx:if="{{showDayDetail}}" bindtap="onCloseDayDetail">
+  <view class="modal-overlay modal-overlay-center" wx:if="{{showDayDetail}}" bindtap="onCloseDayDetail">
     <view class="day-detail-modal" catchtap="noop">
       <view class="detail-date-row">
         <text class="detail-emoji">📅</text>

pages/records/records.wxss

@@ -78,9 +78,21 @@
 
 /* ---- history ---- */
 .history-header {
+  display: flex;
+  justify-content: space-between;
+  align-items: center;
   margin-bottom: 8rpx;
 }
 
+.history-header .section-title {
+  margin-bottom: 0;
+}
+
+.history-hint {
+  font-size: 22rpx;
+  color: #CCC;
+}
+
 .empty-state {
   display: flex;
   flex-direction: column;
@@ -150,19 +162,6 @@
 }
 
 /* ---- day detail popup ---- */
-.modal-overlay {
-  position: fixed;
-  top: 0;
-  left: 0;
-  right: 0;
-  bottom: 0;
-  background: rgba(0, 0, 0, 0.45);
-  z-index: 1000;
-  display: flex;
-  align-items: center;
-  justify-content: center;
-}
-
 .day-detail-modal {
   width: 560rpx;
   background: #fff;

pages/settings/settings.js

@@ -98,5 +98,21 @@ Page({
         wx.showToast({ title: '已复制', icon: 'success', duration: 1500 })
       }
     })
+  },
+
+  onClearData() {
+    wx.showModal({
+      title: '清除数据',
+      content: '将删除所有训练记录和连续打卡数据，此操作不可恢复。确定继续吗？',
+      confirmText: '确定清除',
+      confirmColor: '#E53935',
+      success: (res) => {
+        if (res.confirm) {
+          wx.removeStorageSync('training_records')
+          wx.removeStorageSync('current_streak')
+          wx.showToast({ title: '已清除', icon: 'success', duration: 1500 })
+        }
+      }
+    })
   }
 })

pages/settings/settings.wxml

@@ -92,6 +92,17 @@
     </view>
   </view>
 
+  <!-- 数据管理 -->
+  <view class="card">
+    <view class="section-header">
+      <text class="section-emoji">🗑</text>
+      <text class="section-title">数据管理</text>
+    </view>
+    <button class="btn-danger" bindtap="onClearData">
+      <text>清除所有训练记录</text>
+    </button>
+  </view>
+
   <!-- 关于 -->
   <view class="card about-card">
     <view class="section-header">

pages/timer/timer.js

@@ -41,7 +41,7 @@ Page({
       duration: target,
       remaining: target,
       todayTarget: target,
-      planDay: isFreeMode ? 0 : Math.min(planDay, 99),
+      planDay: isFreeMode ? 0 : planDay,
       isFreeMode
     })
 
@@ -105,6 +105,6 @@ Page({
     storage.updateStreak(today)
 
     wx.showToast({ title: `已记录 ${elapsed}秒`, icon: 'none', duration: 1500 })
-    setTimeout(() => { wx.navigateBack() }, 1500)
+    setTimeout(() => { wx.navigateBack() }, 3000)
   }
 })