feat: improve AI Chat UX, add notebook summary, and fix shared/reminders routing

memento-note/components/chat/chat-messages.tsx

@@ -52,7 +52,7 @@ export function ChatMessages({ messages, isLoading }: ChatMessagesProps) {
             )}
           >
             {msg.role === 'user' ? (
-              <div dir="auto" className="max-w-[85%] md:max-w-[70%] bg-[#f4f4f5] dark:bg-[#2a2d36] text-slate-800 dark:text-slate-100 rounded-3xl rounded-br-md px-6 py-4 shadow-sm border border-slate-200/50 dark:border-white/5">
+              <div dir="auto" className="max-w-[85%] md:max-w-[70%] bg-muted text-foreground rounded-3xl rounded-br-md px-6 py-4 shadow-sm border border-border/50">
                 <div className="prose prose-sm dark:prose-invert max-w-none text-[15px] leading-relaxed">
                   <ReactMarkdown remarkPlugins={[remarkGfm]}>{content}</ReactMarkdown>
                 </div>