ui: add experimental warning to welcome message

Author: dmpantiu

web/templates/index.html

@@ -32,6 +32,12 @@ <h3>Welcome to Eurus</h3>
                 <li>"Show me SST for California coast, Jan 2024"</li>
                 <li>"Plot temperature in the Gulf of Mexico"</li>
             </ul>
+            <p style="margin-top: 10px; font-size: 0.85em; opacity: 0.7;">
+                ⚠️ <strong>Experimental</strong> — This is a research prototype. Please avoid requesting very large
+                datasets
+                (e.g., global multi-year downloads), especially via this HF Space. For heavy workloads, use the
+                📦 Arraylake Code buttons to access data directly.
+            </p>
         </div>
     </div>