feat: 前端UI标题栏优化与配置更新

- 更新.gitignore，添加frontend/.next/忽略
- 优化RecordModal、index、recurring、search、stats页面标题栏样式
- 新增frontend/lib/utils.js工具函数
- 更新useCategories.js钩子
- 添加代码优化计划文档

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

frontend/pages/search.js

@@ -7,12 +7,20 @@ import RecordModal from '../components/RecordModal';
 import { useToast } from '../components/ToastProvider';
 import { useConfirm } from '../components/ConfirmProvider';
 import { useCategories } from '../hooks/useCategories';
+import { formatMoney, parseDateTime, getDatePart } from '../lib/utils';
 
 export default function Search() {
   const router = useRouter();
   const { showToast } = useToast();
   const confirm = useConfirm();
-  const { categories } = useCategories();
+  const { categories, error: categoriesError } = useCategories();
+
+  // 显示分类加载错误
+  useEffect(() => {
+    if (categoriesError) {
+      showToast('分类加载失败', { tone: 'error' });
+    }
+  }, [categoriesError]);
   const [keyword, setKeyword] = useState('');
   const [results, setResults] = useState([]);
   const [loading, setLoading] = useState(false);
@@ -40,6 +48,8 @@ export default function Search() {
   useEffect(() => {
     if (router.isReady && router.query.q) {
       const q = decodeURIComponent(router.query.q);
+      // Skip if already have results for this keyword (prevents double API call)
+      if (keyword === q && results.length > 0) return;
       setKeyword(q);
       // 自动搜索
       const doSearch = async () => {
@@ -56,7 +66,7 @@ export default function Search() {
       };
       doSearch();
     }
-  }, [router.isReady, router.query.q]);
+  }, [router.isReady, router.query.q, keyword, results]);
 
   const handleSearch = async (e) => {
     e.preventDefault();
@@ -81,7 +91,7 @@ export default function Search() {
   };
 
   const openEditModal = (record) => {
-    const [datePart, timePart] = record.date.split(' ');
+    const { datePart, timePart } = parseDateTime(record.date);
     setEditingRecord(record);
     setFormData({
       type: record.type,
@@ -165,12 +175,10 @@ export default function Search() {
     }
   };
 
-  const formatMoney = (num) => (num || 0).toFixed(2);
-
   const groupedResults = useMemo(() => {
     if (!Array.isArray(results)) return {};
     return results.reduce((groups, record) => {
-      const date = record.date.split(' ')[0];
+      const date = getDatePart(record.date);
       if (!groups[date]) groups[date] = [];
       groups[date].push(record);
       return groups;