feat: enhance chat UI and functionality with new scrollbar and animation features

- Added custom scrollbar styles for sources display to improve aesthetics and usability.
- Introduced animations for reasoning steps to enhance user experience during chat interactions.
- Refactored chat page to group thinking messages, improving message handling and display.
- Updated sources display component for better favicon handling and user interaction.

app/globals.css

@@ -296,4 +296,62 @@
 .sidebar-chat-list {
   scrollbar-width: thin;
   scrollbar-color: hsl(var(--muted-foreground) / 0.3) transparent;
-}
+}
+
+/* Minimalista scrollbar para sources */
+.sources-scrollbar {
+  scrollbar-width: thin;
+  scrollbar-color: hsl(var(--muted-foreground) / 0.2) transparent;
+}
+
+.sources-scrollbar::-webkit-scrollbar {
+  height: 4px;
+}
+
+.sources-scrollbar::-webkit-scrollbar-track {
+  background: transparent;
+  border-radius: 2px;
+}
+
+.sources-scrollbar::-webkit-scrollbar-thumb {
+  background: hsl(var(--muted-foreground) / 0.2);
+  border-radius: 2px;
+  transition: background 0.2s ease;
+}
+
+.sources-scrollbar::-webkit-scrollbar-thumb:hover {
+  background: hsl(var(--muted-foreground) / 0.35);
+}
+
+/* Ocultar scrollbar quando não há overflow */
+.sources-scrollbar:not(:hover)::-webkit-scrollbar-thumb {
+  background: transparent;
+}
+
+/* Reasoning Chain animations */
+@keyframes reasoning-fade-in {
+  from { 
+    opacity: 0; 
+    transform: translateY(4px); 
+  }
+  to { 
+    opacity: 1; 
+    transform: translateY(0); 
+  }
+}
+
+.reasoning-step {
+  animation: reasoning-fade-in 0.3s ease-out forwards;
+  opacity: 0;
+}
+
+/* Staggered reveal para steps */
+.reasoning-step:nth-child(1) { animation-delay: 0ms; }
+.reasoning-step:nth-child(2) { animation-delay: 100ms; }
+.reasoning-step:nth-child(3) { animation-delay: 200ms; }
+.reasoning-step:nth-child(4) { animation-delay: 300ms; }
+.reasoning-step:nth-child(5) { animation-delay: 400ms; }
+.reasoning-step:nth-child(6) { animation-delay: 500ms; }
+.reasoning-step:nth-child(7) { animation-delay: 600ms; }
+.reasoning-step:nth-child(8) { animation-delay: 700ms; }
+.reasoning-step:nth-child(n+9) { animation-delay: 800ms; }