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.Test/WebApi.Test.csproj

@@ -19,5 +19,6 @@
     <ItemGroup>
         <ProjectReference Include="..\Application\Application.csproj" />
         <ProjectReference Include="..\Service\Service.csproj" />
+        <ProjectReference Include="..\WebApi\WebApi.csproj" />
     </ItemGroup>
 </Project>