feat: 统计页面添加分类筛选与搜索优化

- 统计页面添加分类多选筛选功能
- 点击分类可跳转到搜索页面查看详情
- 搜索页面添加 URL 同步与自动搜索
- 提取 useCategories hook 消除重复代码
- 修复自定义分类图标显示问题
- 添加 useMemo 优化计算性能

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

frontend/hooks/useCategories.js

@@ -0,0 +1,45 @@
+import { useState, useEffect } from 'react';
+import { getCategories, isLoggedIn } from '../lib/api';
+import { DEFAULT_CATEGORIES } from '../lib/categories';
+
+export function useCategories() {
+  const [categories, setCategories] = useState(DEFAULT_CATEGORIES);
+  const [loading, setLoading] = useState(true);
+
+  useEffect(() => {
+    if (!isLoggedIn()) {
+      setLoading(false);
+      return;
+    }
+
+    const loadCategories = async () => {
+      try {
+        const categoriesData = await getCategories();
+        if (categoriesData) {
+          setCategories({
+            expense: [
+              ...DEFAULT_CATEGORIES.expense,
+              ...(categoriesData.expense || []).filter(
+                c => !DEFAULT_CATEGORIES.expense.some(d => d.name === c.name)
+              )
+            ],
+            income: [
+              ...DEFAULT_CATEGORIES.income,
+              ...(categoriesData.income || []).filter(
+                c => !DEFAULT_CATEGORIES.income.some(d => d.name === c.name)
+              )
+            ],
+          });
+        }
+      } catch (err) {
+        console.error(err);
+      } finally {
+        setLoading(false);
+      }
+    };
+
+    loadCategories();
+  }, []);
+
+  return { categories, loading };
+}