refactor: 简化URL结构

将`HashRouter`替换为更现代的`BrowserRouter`，移除`#`片段以简化URL结构。

BillNote_frontend/src/App.tsx

@@ -2,7 +2,7 @@ import './App.css'
 import { HomePage } from './pages/HomePage/Home.tsx'
 import { useTaskPolling } from '@/hooks/useTaskPolling.ts'
 import SettingPage from './pages/SettingPage/index.tsx'
-import { BrowserRouter, HashRouter, Navigate, Routes } from 'react-router-dom'
+import { BrowserRouter, Navigate, Routes } from 'react-router-dom'
 import { Route } from 'react-router-dom'
 import Index from '@/pages/Index.tsx'
 import NotFoundPage from '@/pages/NotFoundPage'
@@ -43,7 +43,7 @@ function App() {
   // 后端已初始化，渲染主应用
   return (
     <>
-      <HashRouter>
+      <BrowserRouter>
         <Routes>
           <Route path="/" element={<Index />}>
             <Route index element={<HomePage />} />
@@ -62,7 +62,7 @@ function App() {
             <Route path="*" element={<NotFoundPage />} />
           </Route>
         </Routes>
-      </HashRouter>
+      </BrowserRouter>
     </>
   )
 }