refactor: 整合财务系统到主应用并重构后端架构

主要变更:
- 将独立的 web-finance 应用整合到 web-antd 主应用中
- 重命名 backend-mock 为 backend,增强后端功能
- 新增财务模块 API 端点(账户、预算、类别、交易)
- 增强财务仪表板和报表功能
- 添加 SQLite 数据存储支持和财务数据导入脚本
- 优化路由结构,删除冗余的 finance-system 模块

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

apps/backend/api/finance/exchange-rates.get.ts

@@ -0,0 +1,30 @@
+import { getQuery } from 'h3';
+
+import { listExchangeRates } from '~/utils/finance-metadata';
+import { useResponseSuccess } from '~/utils/response';
+
+export default defineEventHandler(async (event) => {
+  const query = getQuery(event);
+  const fromCurrency = query.from as string | undefined;
+  const toCurrency = query.to as string | undefined;
+  const date = query.date as string | undefined;
+
+  let rates = listExchangeRates();
+
+  if (fromCurrency) {
+    rates = rates.filter((rate) => rate.fromCurrency === fromCurrency);
+  }
+
+  if (toCurrency) {
+    rates = rates.filter((rate) => rate.toCurrency === toCurrency);
+  }
+
+  if (date) {
+    rates = rates.filter((rate) => rate.date === date);
+  } else if (rates.length > 0) {
+    const latestDate = rates.reduce((max, rate) => (rate.date > max ? rate.date : max), rates[0].date);
+    rates = rates.filter((rate) => rate.date === latestDate);
+  }
+
+  return useResponseSuccess(rates);
+});