chore: migrate remaining ECharts components to Chart.js

- Migrated 4 components from ECharts to Chart.js:
  * MonthlyExpenseCard.vue (折线图)
  * DailyTrendChart.vue (双系列折线图)
  * ExpenseCategoryCard.vue (环形图)
  * BudgetChartAnalysis.vue (仪表盘 + 多种图表)

- Removed all ECharts imports and environment variable switches
- Unified all charts to use BaseChart.vue component
- Build verified: pnpm build success ✓
- No echarts imports remaining ✓

Refs: openspec/changes/migrate-remaining-echarts-to-chartjs

Application/Dto/Icon/IconCandidateDto.cs

@@ -0,0 +1,22 @@
+namespace Application.Dto.Icon;
+
+/// <summary>
+/// 图标候选对象
+/// </summary>
+public record IconCandidateDto
+{
+    /// <summary>
+    /// 图标集名称
+    /// </summary>
+    public string CollectionName { get; init; } = string.Empty;
+
+    /// <summary>
+    /// 图标名称
+    /// </summary>
+    public string IconName { get; init; } = string.Empty;
+
+    /// <summary>
+    /// 图标标识符（格式：{collectionName}:{iconName}，如"mdi:home"）
+    /// </summary>
+    public string IconIdentifier { get; init; } = string.Empty;
+}

Application/Dto/Icon/SearchIconsRequest.cs

@@ -0,0 +1,12 @@
+namespace Application.Dto.Icon;
+
+/// <summary>
+/// 搜索图标请求
+/// </summary>
+public record SearchIconsRequest
+{
+    /// <summary>
+    /// 搜索关键字数组
+    /// </summary>
+    public List<string> Keywords { get; init; } = [];
+}

Application/Dto/Icon/SearchKeywordsRequest.cs

@@ -0,0 +1,12 @@
+namespace Application.Dto.Icon;
+
+/// <summary>
+/// 搜索关键字生成请求
+/// </summary>
+public record SearchKeywordsRequest
+{
+    /// <summary>
+    /// 分类名称
+    /// </summary>
+    public string CategoryName { get; init; } = string.Empty;
+}

Application/Dto/Icon/SearchKeywordsResponse.cs

@@ -0,0 +1,12 @@
+namespace Application.Dto.Icon;
+
+/// <summary>
+/// 搜索关键字生成响应
+/// </summary>
+public record SearchKeywordsResponse
+{
+    /// <summary>
+    /// 搜索关键字数组
+    /// </summary>
+    public List<string> Keywords { get; init; } = [];
+}

Application/Dto/Icon/UpdateCategoryIconRequest.cs

@@ -0,0 +1,17 @@
+namespace Application.Dto.Icon;
+
+/// <summary>
+/// 更新分类图标请求
+/// </summary>
+public record UpdateCategoryIconRequest
+{
+    /// <summary>
+    /// 分类ID
+    /// </summary>
+    public long CategoryId { get; init; }
+
+    /// <summary>
+    /// 图标标识符（格式：{collectionName}:{iconName}，如"mdi:home"）
+    /// </summary>
+    public string IconIdentifier { get; init; } = string.Empty;
+}