更新主题样式，添加边框颜色变量；优化弹窗背景和标题样式；调整月度数据加载格式；改进图表初始化逻辑

Web/src/components/CategoryBillPopup.vue

@@ -343,6 +343,7 @@ watch(visible, (newValue) => {
   padding: var(--spacing-2xl);
   padding-bottom: var(--spacing-lg);
   border-bottom: 1px solid var(--border-color);
+  background: var(--bg-secondary);
 }
 
 .popup-title {
@@ -352,6 +353,7 @@ watch(visible, (newValue) => {
   color: var(--text-primary);
   margin: 0;
   text-align: center;
+  letter-spacing: -0.02em;
 }
 
 .popup-subtitle {
@@ -389,6 +391,7 @@ watch(visible, (newValue) => {
   border-radius: var(--radius-md);
   cursor: pointer;
   transition: opacity 0.2s;
+  margin-top: 10px;
 }
 
 .txn-card:active {

Web/src/components/PopupContainer.vue

@@ -1,4 +1,4 @@
-<!-- eslint-disable vue/no-v-html -->
+<!-- eslint-disable vue/no-v-html -->
 <template>
   <van-popup
     v-model:show="visible"
@@ -111,7 +111,7 @@ const hasActions = computed(() => !!slots['header-actions'])
 .popup-header-fixed {
   flex-shrink: 0;
   padding: 16px;
-  background-color: var(--van-background-2);
+  background: linear-gradient(180deg, var(--van-background) 0%, var(--van-background-2) 100%);
   border-bottom: 1px solid var(--van-border-color);
   position: sticky;
   top: 0;
@@ -138,10 +138,11 @@ const hasActions = computed(() => !!slots['header-actions'])
 
 .popup-title {
   font-size: 16px;
-  font-weight: 500;
+  font-weight: 600;
   margin: 0;
   text-align: center;
   color: var(--van-text-color);
+  letter-spacing: -0.02em;
   /*超出长度*/
   overflow: hidden;
   text-overflow: ellipsis;