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

Service/IconSearch/IIconSearchService.cs

@@ -0,0 +1,29 @@
+namespace Service.IconSearch;
+
+/// <summary>
+/// 图标搜索服务接口
+/// </summary>
+public interface IIconSearchService
+{
+    /// <summary>
+    /// 生成搜索关键字
+    /// </summary>
+    /// <param name="categoryName">分类名称</param>
+    /// <returns>搜索关键字数组</returns>
+    Task<List<string>> GenerateSearchKeywordsAsync(string categoryName);
+
+    /// <summary>
+    /// 搜索图标并返回候选列表
+    /// </summary>
+    /// <param name="keywords">搜索关键字数组</param>
+    /// <param name="limit">每个关键字返回的最大图标数量</param>
+    /// <returns>图标候选列表</returns>
+    Task<List<IconCandidate>> SearchIconsAsync(List<string> keywords, int limit = 20);
+
+    /// <summary>
+    /// 更新分类图标
+    /// </summary>
+    /// <param name="categoryId">分类ID</param>
+    /// <param name="iconIdentifier">图标标识符</param>
+    Task UpdateCategoryIconAsync(long categoryId, string iconIdentifier);
+}

Service/IconSearch/IIconifyApiService.cs

@@ -0,0 +1,15 @@
+namespace Service.IconSearch;
+
+/// <summary>
+/// Iconify API服务接口
+/// </summary>
+public interface IIconifyApiService
+{
+    /// <summary>
+    /// 搜索图标
+    /// </summary>
+    /// <param name="keywords">搜索关键字数组</param>
+    /// <param name="limit">每个关键字返回的最大图标数量</param>
+    /// <returns>图标候选列表</returns>
+    Task<List<IconCandidate>> SearchIconsAsync(List<string> keywords, int limit = 20);
+}

Service/IconSearch/ISearchKeywordGeneratorService.cs

@@ -0,0 +1,14 @@
+namespace Service.IconSearch;
+
+/// <summary>
+/// 搜索关键字生成服务接口
+/// </summary>
+public interface ISearchKeywordGeneratorService
+{
+    /// <summary>
+    /// 根据分类名称生成搜索关键字
+    /// </summary>
+    /// <param name="categoryName">分类名称</param>
+    /// <returns>搜索关键字数组</returns>
+    Task<List<string>> GenerateKeywordsAsync(string categoryName);
+}

Service/IconSearch/IconCandidate.cs

@@ -0,0 +1,22 @@
+namespace Service.IconSearch;
+
+/// <summary>
+/// 图标候选对象
+/// </summary>
+public record IconCandidate
+{
+    /// <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}）
+    /// </summary>
+    public string IconIdentifier => $"{CollectionName}:{IconName}";
+}

Service/IconSearch/IconSearchService.cs

@@ -0,0 +1,48 @@
+namespace Service.IconSearch;
+
+public class IconSearchService(
+    ISearchKeywordGeneratorService keywordGeneratorService,
+    IIconifyApiService iconifyApiService,
+    ITransactionCategoryRepository categoryRepository,
+    ILogger<IconSearchService> logger
+) : IIconSearchService
+{
+    public async Task<List<string>> GenerateSearchKeywordsAsync(string categoryName)
+    {
+        var keywords = await keywordGeneratorService.GenerateKeywordsAsync(categoryName);
+        return keywords;
+    }
+
+    public async Task<List<IconCandidate>> SearchIconsAsync(List<string> keywords, int limit = 20)
+    {
+        if (keywords == null || keywords.Count == 0)
+        {
+            logger.LogWarning("搜索关键字为空");
+            return [];
+        }
+
+        var icons = await iconifyApiService.SearchIconsAsync(keywords, limit);
+        logger.LogInformation("搜索到 {Count} 个图标候选", icons.Count);
+        return icons;
+    }
+
+    public async Task UpdateCategoryIconAsync(long categoryId, string iconIdentifier)
+    {
+        if (string.IsNullOrWhiteSpace(iconIdentifier))
+        {
+            throw new ArgumentException("图标标识符不能为空", nameof(iconIdentifier));
+        }
+
+        var category = await categoryRepository.GetByIdAsync(categoryId);
+        if (category == null)
+        {
+            throw new Exception($"分类不存在，ID：{categoryId}");
+        }
+
+        category.Icon = iconIdentifier;
+        category.IconKeywords = null;
+        await categoryRepository.UpdateAsync(category);
+
+        logger.LogInformation("更新分类 {CategoryId} 的图标为 {IconIdentifier}", categoryId, iconIdentifier);
+    }
+}

Service/IconSearch/IconifyApiService.cs

@@ -0,0 +1,117 @@
+namespace Service.IconSearch;
+
+/// <summary>
+/// Iconify API 响应
+/// 实际 API 返回的图标是字符串数组，格式为 "collection:iconName"
+/// 例如：["mdi:home", "svg-spinners:wind-toy"]
+/// </summary>
+public record IconifyApiResponse
+{
+    [JsonPropertyName("icons")]
+    public List<string>? Icons { get; init; }
+}
+
+public record IconifySettings
+{
+    public string ApiUrl { get; init; } = "https://api.iconify.design/search";
+    public int DefaultLimit { get; init; } = 20;
+    public int MaxRetryCount { get; init; } = 3;
+    public int RetryDelayMs { get; init; } = 1000;
+}
+
+public class IconifyApiService(
+    IOptions<IconifySettings> settings,
+    ILogger<IconifyApiService> logger
+) : IIconifyApiService
+{
+    private readonly HttpClient _httpClient = new();
+    private readonly IconifySettings _settings = settings.Value;
+
+    public async Task<List<IconCandidate>> SearchIconsAsync(List<string> keywords, int limit = 20)
+    {
+        var allIcons = new List<IconCandidate>();
+        var actualLimit = limit > 0 ? limit : _settings.DefaultLimit;
+
+        foreach (var keyword in keywords)
+        {
+            try
+            {
+                var icons = await SearchIconsByKeywordAsync(keyword, actualLimit);
+                allIcons.AddRange(icons);
+            }
+            catch (Exception ex)
+            {
+                logger.LogError(ex, "搜索图标失败，关键字：{Keyword}", keyword);
+            }
+        }
+
+        return allIcons;
+    }
+
+    private async Task<List<IconCandidate>> SearchIconsByKeywordAsync(string keyword, int limit)
+    {
+        var url = $"{_settings.ApiUrl}?query={Uri.EscapeDataString(keyword)}&limit={limit}";
+        var response = await CallApiWithRetryAsync(url);
+
+        if (string.IsNullOrEmpty(response))
+        {
+            return [];
+        }
+
+        var apiResponse = JsonSerializer.Deserialize<IconifyApiResponse>(response);
+        if (apiResponse?.Icons == null)
+        {
+            return [];
+        }
+
+        // 解析字符串格式 "collection:iconName" 为 IconCandidate
+        var candidates = apiResponse.Icons
+            .Select(iconStr =>
+            {
+                var parts = iconStr.Split(':', 2);
+                if (parts.Length != 2)
+                {
+                    logger.LogWarning("无效的图标标识符格式：{IconStr}", iconStr);
+                    return null;
+                }
+
+                return new IconCandidate
+                {
+                    CollectionName = parts[0],
+                    IconName = parts[1]
+                };
+            })
+            .Where(c => c != null)
+            .Cast<IconCandidate>()
+            .ToList();
+
+        return candidates;
+    }
+
+    private async Task<string> CallApiWithRetryAsync(string url)
+    {
+        var retryCount = 0;
+        var delay = _settings.RetryDelayMs;
+
+        while (retryCount < _settings.MaxRetryCount)
+        {
+            try
+            {
+                var response = await _httpClient.GetAsync(url);
+                response.EnsureSuccessStatusCode();
+
+                return await response.Content.ReadAsStringAsync();
+            }
+            catch (HttpRequestException ex) when (retryCount < _settings.MaxRetryCount - 1)
+            {
+                logger.LogWarning(ex, "Iconify API调用失败，等待 {DelayMs}ms 后重试（{RetryCount}/{MaxRetryCount}）",
+                    delay, retryCount + 1, _settings.MaxRetryCount);
+                await Task.Delay(delay);
+                delay *= 2;
+                retryCount++;
+            }
+        }
+
+        throw new HttpRequestException($"Iconify API调用失败，已重试 {_settings.MaxRetryCount} 次");
+    }
+}

Service/IconSearch/SearchKeywordGeneratorService.cs

@@ -0,0 +1,94 @@
+using Service.AI;
+
+namespace Service.IconSearch;
+
+public record SearchKeywordSettings
+{
+    public string KeywordPromptTemplate { get; init; } = 
+        "为以下中文分类名称生成3-5个相关的英文搜索关键字，用于搜索图标：{categoryName}。" +
+        "输出格式为JSON数组，例如：[\"food\", \"restaurant\", \"dining\"]。";
+}
+
+public class SearchKeywordGeneratorService(
+    IOpenAiService openAiService,
+    IOptions<SearchKeywordSettings> settings,
+    ILogger<SearchKeywordGeneratorService> logger
+) : ISearchKeywordGeneratorService
+{
+    private readonly SearchKeywordSettings _settings = settings.Value;
+
+    public async Task<List<string>> GenerateKeywordsAsync(string categoryName)
+    {
+        if (string.IsNullOrWhiteSpace(categoryName))
+        {
+            logger.LogWarning("分类名称为空，无法生成搜索关键字");
+            return [];
+        }
+
+        try
+        {
+            var prompt = _settings.KeywordPromptTemplate.Replace("{categoryName}", categoryName);
+            var response = await openAiService.ChatAsync(prompt, timeoutSeconds: 15);
+
+            if (string.IsNullOrEmpty(response))
+            {
+                logger.LogWarning("AI未返回搜索关键字，分类：{CategoryName}", categoryName);
+                return [];
+            }
+
+            var keywords = ParseKeywordsFromResponse(response);
+            logger.LogInformation("为分类 {CategoryName} 生成了 {Count} 个搜索关键字：{Keywords}",
+                categoryName, keywords.Count, string.Join(", ", keywords));
+
+            return keywords;
+        }
+        catch (Exception ex)
+        {
+            logger.LogError(ex, "生成搜索关键字失败，分类：{CategoryName}", categoryName);
+            return [];
+        }
+    }
+
+    private List<string> ParseKeywordsFromResponse(string response)
+    {
+        try
+        {
+            var jsonNode = JsonNode.Parse(response);
+            if (jsonNode is JsonArray arrayNode)
+            {
+                var keywords = new List<string>();
+                foreach (var item in arrayNode)
+                {
+                    if (item is JsonValue value && value.TryGetValue(out string keyword))
+                    {
+                        keywords.Add(keyword);
+                    }
+                }
+                return keywords;
+            }
+            else if (jsonNode is JsonObject jsonObject)
+            {
+                if (jsonObject.TryGetPropertyValue("keywords", out var keywordsNode) && keywordsNode is JsonArray arrayNode2)
+                {
+                    var keywords = new List<string>();
+                    foreach (var item in arrayNode2)
+                    {
+                        if (item is JsonValue value && value.TryGetValue(out string keyword))
+                        {
+                            keywords.Add(keyword);
+                        }
+                    }
+                    return keywords;
+                }
+            }
+
+            logger.LogWarning("无法解析AI响应为关键字数组：{Response}", response);
+            return [];
+        }
+        catch (Exception ex)
+        {
+            logger.LogError(ex, "解析AI响应失败：{Response}", response);
+            return [];
+        }
+    }
+}