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/components/chat/ChatMessage.tsx

@@ -10,14 +10,14 @@ export function ChatMessage({ message }: { message: Message }) {
     <div className={cn('mb-4 flex', isUser ? 'justify-end' : 'justify-start')}>
       <div
         className={cn(
-          'max-w-[80%] rounded-lg px-4 py-2.5',
+          'max-w-[80%] rounded-xl px-4 py-2.5',
           isUser
-            ? 'bg-zinc-800 text-zinc-100'
-            : 'bg-zinc-900 text-zinc-300 border border-zinc-800'
+            ? 'bg-indigo-600 text-white'
+            : 'bg-white text-zinc-700 border border-zinc-200 shadow-sm'
         )}
       >
         {isEmpty ? (
-          <span className="text-zinc-600 italic text-xs">...</span>
+          <span className="text-zinc-400 italic text-xs">...</span>
         ) : isUser ? (
           <p className="text-sm leading-relaxed whitespace-pre-wrap">{message.content}</p>
         ) : (