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/overview/overview.wxml

@@ -1,64 +1,73 @@
 <view class="container">
-  <!-- 顶部控制区 -->
-  <view class="card header-card">
-    <view class="header-top">
-      <text class="header-title">📊 汇率总览</text>
+  <!-- 控制区 -->
+  <view class="card ctrl-card">
+    <view class="ctrl-top">
+      <text class="ctrl-title">汇率总览</text>
+      <view class="ctrl-badge" wx:if="{{updatedAt}}">
+        <text class="badge-text">{{updatedAt}}</text>
+      </view>
     </view>
 
-    <view class="control-row">
-      <text class="control-label">基准</text>
-      <picker range="{{pickerData}}" value="{{baseIndex}}" bindchange="handleBaseChange">
-        <view class="base-tag">
-          <text class="base-tag-text">{{pickerData[baseIndex]}}</text>
-          <text class="tag-arrow">▼</text>
-        </view>
-      </picker>
+    <view class="ctrl-row">
+      <text class="ctrl-label">基准货币</text>
+      <view class="ctrl-chip" bindtap="openBasePicker">
+        <text class="chip-text">{{pickerData[baseIndex]}}</text>
+        <text class="chip-arrow">›</text>
+      </view>
     </view>
 
-    <view class="control-row">
-      <text class="control-label">金额</text>
+    <view class="ctrl-row">
+      <text class="ctrl-label">换算金额</text>
       <input
-        class="amount-input"
+        class="ctrl-input"
         type="digit"
         value="{{amount}}"
         bindinput="handleAmountInput"
-        placeholder="输入金额"
-        placeholder-class="amount-placeholder"
+        placeholder="100"
+        placeholder-class="ctrl-placeholder"
       />
     </view>
-
-    <view class="updated-at" wx:if="{{updatedAt}}">{{updatedAt}} 更新</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>
 
-  <!-- 加载中 -->
-  <view class="loading-card" wx:if="{{loading}}">
-    <text>正在获取汇率数据...</text>
+  <!-- 加载 -->
+  <view class="loading-wrap" wx:if="{{loading}}">
+    <view class="loading-dot"></view>
+    <text class="loading-text">加载中</text>
   </view>
 
-  <!-- 汇率列表 -->
-  <view class="card list-card" wx:if="{{list.length}}">
+  <!-- 列表 -->
+  <view class="list-wrap" wx:if="{{list.length}}">
     <view
-      class="rate-item"
+      class="card rate-row"
       wx:for="{{list}}"
       wx:key="code"
     >
-      <view class="rate-left">
-        <text class="rate-flag">{{item.flag}}</text>
-        <view class="rate-info">
-          <text class="rate-code">{{item.code}}</text>
-          <text class="rate-name">{{item.name}}</text>
+      <view class="row-left">
+        <view class="flag-circle">
+          <text class="flag-emoji">{{item.flag}}</text>
+        </view>
+        <view class="row-info">
+          <text class="row-code">{{item.code}}</text>
+          <text class="row-name">{{item.name}}</text>
         </view>
       </view>
-      <view class="rate-right">
-        <text class="rate-value">{{item.converted}}</text>
-        <text class="rate-unit">1 = {{item.unitRate}}</text>
+      <view class="row-right">
+        <text class="row-value">{{item.converted}}</text>
+        <text class="row-unit">1 = {{item.unitRate}}</text>
       </view>
     </view>
   </view>
 </view>
+
+<currency-picker
+  show="{{showPicker}}"
+  list="{{pickerData}}"
+  current="{{baseIndex}}"
+  bind:select="handlePickerSelect"
+  bind:close="handlePickerClose"
+/>