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

WebApi/Controllers/IconController.cs

@@ -0,0 +1,72 @@
+using Application.Dto.Icon;
+using Application;
+using Service.IconSearch;
+
+namespace WebApi.Controllers;
+
+/// <summary>
+/// 图标管理控制器
+/// </summary>
+[ApiController]
+[Route("api/icons")]
+public class IconController(
+    IIconSearchService iconSearchService,
+    ILogger<IconController> logger
+) : ControllerBase
+{
+    /// <summary>
+    /// 生成搜索关键字
+    /// </summary>
+    /// <param name="request">搜索关键字生成请求</param>
+    /// <returns>搜索关键字生成响应</returns>
+    [HttpPost("search-keywords")]
+    public async Task<BaseResponse<SearchKeywordsResponse>> GenerateSearchKeywordsAsync(
+        [FromBody] SearchKeywordsRequest request)
+    {
+        var keywords = await iconSearchService.GenerateSearchKeywordsAsync(request.CategoryName);
+        logger.LogInformation("为分类 {CategoryName} 生成了 {Count} 个搜索关键字",
+            request.CategoryName, keywords.Count);
+
+        return new SearchKeywordsResponse { Keywords = keywords }.Ok();
+    }
+
+    /// <summary>
+    /// 搜索图标
+    /// </summary>
+    /// <param name="request">搜索图标请求</param>
+    /// <returns>图标候选列表响应</returns>
+    [HttpPost("search")]
+    public async Task<BaseResponse<List<IconCandidateDto>>> SearchIconsAsync(
+        [FromBody] SearchIconsRequest request)
+    {
+        var icons = await iconSearchService.SearchIconsAsync(request.Keywords, limit: 20);
+        logger.LogInformation("搜索到 {Count} 个图标候选", icons.Count);
+
+        var iconDtos = icons.Select(i => new IconCandidateDto
+        {
+            CollectionName = i.CollectionName,
+            IconName = i.IconName,
+            IconIdentifier = i.IconIdentifier
+        }).ToList();
+
+        return iconDtos.Ok();
+    }
+
+    /// <summary>
+    /// 更新分类图标
+    /// </summary>
+    /// <param name="categoryId">分类ID</param>
+    /// <param name="request">更新分类图标请求</param>
+    /// <returns>操作结果</returns>
+    [HttpPut("categories/{categoryId}/icon")]
+    public async Task<BaseResponse> UpdateCategoryIconAsync(
+        long categoryId,
+        [FromBody] UpdateCategoryIconRequest request)
+    {
+        await iconSearchService.UpdateCategoryIconAsync(categoryId, request.IconIdentifier);
+        logger.LogInformation("更新分类 {CategoryId} 的图标为 {IconIdentifier}",
+            categoryId, request.IconIdentifier);
+
+        return "更新分类图标成功".Ok();
+    }
+}