fix: chat response visibility and backend fallback

backend/app/routers/analysis.py

@@ -53,4 +53,6 @@ async def agent_chat(request: ChatRequest):
     )
     
     response = await call_gemini_with_model(prompt, request.model)
+    if not response:
+        response = "Lo siento, tuve un problema procesando tu solicitud. ¿Podrías intentar de nuevo?"
     return {"response": response}

frontend/components/AgentChat.tsx

@@ -44,6 +44,7 @@ export default function AgentChat({ tender, companyProfile }: Props) {
   ];
 
   const simulateTyping = (text: string, agentName: string) => {
+    if (!text) return; // Don't simulate empty text
     setIsTyping(true);
     let currentText = "";
     const words = text.split(" ");
@@ -64,7 +65,7 @@ export default function AgentChat({ tender, companyProfile }: Props) {
         clearInterval(interval);
         setIsTyping(false);
       }
-    }, 40);
+    }, 20); // Faster typing
   };
 
   useEffect(() => {
@@ -164,17 +165,17 @@ export default function AgentChat({ tender, companyProfile }: Props) {
         )}
         {messages.map((msg, i) => (
           <div key={i} className={`flex ${msg.role === 'user' ? 'justify-end' : 'justify-start'}`}>
-            <div className={`max-w-[80%] rounded-2xl px-5 py-3 text-sm ${
+            <div className={`max-w-[80%] rounded-2xl px-6 py-4 text-[13px] shadow-lg ${
               msg.role === 'user' 
                 ? 'bg-purple-600 text-white rounded-tr-none' 
-                : 'bg-white/10 text-slate-200 border border-white/10 rounded-tl-none'
+                : 'bg-white/10 text-white border border-white/20 rounded-tl-none backdrop-blur-md'
             }`}>
               {msg.role === 'assistant' && (
                 <div className="text-[10px] font-black uppercase text-purple-400 mb-1 tracking-widest">
                   {msg.agent}
                 </div>
               )}
-              <p className="leading-relaxed whitespace-pre-wrap">{msg.content}</p>
+              <p className="leading-relaxed whitespace-pre-wrap min-h-[1.25em] text-white/90">{msg.content}</p>
             </div>
           </div>
         ))}