ui: 暗色金融风重构 + 自定义货币选择器

- 深色主题：深蓝背景 + 毛玻璃卡片 + 金色结果数字
- 自定义底部弹窗货币选择器，替换原生白色 Picker
- 换算卡片内容居中竖排布局
- 汇率信息条改为竖排独立卡片
- 实时脉冲徽章 + 蓝紫渐变互换按钮

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

miniprogram/pages/index/index.wxml

@@ -1,76 +1,84 @@
 <view class="container">
-  <!-- 顶部标题区 -->
+  <!-- 顶部 -->
   <view class="hero">
-    <view class="hero-title">💱 汇率换算</view>
-    <view class="hero-desc" wx:if="{{updatedAt}}">{{updatedAt}} 更新</view>
-    <view class="hero-desc" wx:if="{{loading}}">正在获取最新汇率...</view>
+    <view class="hero-row">
+      <view class="hero-title">汇率换算</view>
+      <view class="hero-badge" wx:if="{{!loading}}">
+        <view class="badge-dot"></view>
+        <text class="badge-text">实时</text>
+      </view>
+    </view>
+    <view class="hero-desc" wx:if="{{updatedAt}}">{{updatedAt}}</view>
+    <view class="hero-desc" wx:if="{{loading}}">正在同步汇率数据...</view>
   </view>
 
   <!-- 换算主卡片 -->
   <view class="card converter-card">
     <!-- 源币种 -->
     <view class="currency-block from-block">
-      <picker range="{{pickerData}}" value="{{fromIndex}}" bindchange="handleFromChange">
-        <view class="currency-tag">
-          <text class="currency-tag-text">{{pickerData[fromIndex]}}</text>
-          <text class="tag-arrow">▼</text>
-        </view>
-      </picker>
+      <text class="block-label">从</text>
+      <view class="currency-chip" bindtap="openFromPicker">
+        <text class="chip-text">{{pickerData[fromIndex]}}</text>
+        <text class="chip-arrow">›</text>
+      </view>
       <input
         class="amount-input"
         type="digit"
         value="{{amount}}"
         bindinput="handleAmountInput"
-        placeholder="输入金额"
+        placeholder="0.00"
         placeholder-class="amount-placeholder"
       />
     </view>
 
-    <!-- 互换按钮 -->
-    <view class="swap-wrapper">
-      <view class="swap-line"></view>
-      <view class="swap-btn" bindtap="handleSwap">
+    <!-- 互换 -->
+    <view class="swap-zone" bindtap="handleSwap">
+      <view class="swap-track"></view>
+      <view class="swap-btn">
         <text class="swap-icon">⇅</text>
       </view>
-      <view class="swap-line"></view>
+      <view class="swap-track"></view>
     </view>
 
     <!-- 目标币种 -->
     <view class="currency-block to-block">
-      <picker range="{{pickerData}}" value="{{toIndex}}" bindchange="handleToChange">
-        <view class="currency-tag">
-          <text class="currency-tag-text">{{pickerData[toIndex]}}</text>
-          <text class="tag-arrow">▼</text>
-        </view>
-      </picker>
-      <view class="result-display">{{result || '—'}}</view>
+      <text class="block-label">到</text>
+      <view class="currency-chip" bindtap="openToPicker">
+        <text class="chip-text">{{pickerData[toIndex]}}</text>
+        <text class="chip-arrow">›</text>
+      </view>
+      <view class="result-amount">{{result || '0.00'}}</view>
     </view>
   </view>
 
-  <!-- 单位汇率卡片 -->
-  <view class="card rate-card" wx:if="{{unitRate}}">
-    <view class="rate-row">
-      <text class="rate-dot from-dot"></text>
+  <!-- 汇率信息 -->
+  <view class="rate-list" wx:if="{{unitRate}}">
+    <view class="card rate-item">
       <text class="rate-text">{{unitRate}}</text>
     </view>
-    <view class="rate-row">
-      <text class="rate-dot to-dot"></text>
+    <view class="card rate-item">
       <text class="rate-text">{{reverseRate}}</text>
     </view>
   </view>
 
-  <!-- 错误提示 -->
+  <!-- 错误 -->
   <view class="card error-card" wx:if="{{error}}">
-    <text class="error-icon">⚠</text>
     <text class="error-text">{{error}}</text>
   </view>
 
-  <!-- 汇率总览入口 -->
-  <view class="card overview-entry" bindtap="goOverview">
-    <view class="overview-left">
-      <text class="overview-icon">📊</text>
-      <text class="overview-label">查看汇率总览</text>
+  <!-- 总览入口 -->
+  <view class="overview-btn" bindtap="goOverview">
+    <view class="overview-inner">
+      <text class="overview-label">查看全部汇率</text>
+      <text class="overview-arrow">→</text>
     </view>
-    <text class="overview-arrow">›</text>
   </view>
 </view>
+
+<currency-picker
+  show="{{showPicker}}"
+  list="{{pickerData}}"
+  current="{{pickerTarget === 'from' ? fromIndex : toIndex}}"
+  bind:select="handlePickerSelect"
+  bind:close="handlePickerClose"
+/>