refactor(web): router-based navigation, light theme, form config

- Replace Zustand activeView with React Router (NavLink + Routes)
- White/light modern theme with indigo accents
- Sidebar with Chinese labels under icons
- ConfigForm with individual form fields (no JSON textareas)
- Account switching with context injection into chat
- Fix duplicate conversation creation with useRef guard
- Asset gallery: smaller 6-column grid with date labels
- All components updated to light color scheme

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

web/client/src/main.tsx

@@ -1,10 +1,13 @@
 import React from 'react';
 import ReactDOM from 'react-dom/client';
+import { BrowserRouter } from 'react-router-dom';
 import App from './App';
 import './index.css';
 
 ReactDOM.createRoot(document.getElementById('root')!).render(
   <React.StrictMode>
-    <App />
+    <BrowserRouter>
+      <App />
+    </BrowserRouter>
   </React.StrictMode>
 );