Fix: Replace hardcoded localhost API URL with env var

frontend/src/components/ChatPanel.tsx

@@ -479,7 +479,8 @@ export default function ChatPanel({ onMapUpdate, layers = [] }: ChatPanelProps)
 
         try {
             const history = messages.map(m => ({ role: m.role, content: m.content }));
-            const response = await fetch("http://localhost:8000/api/v1/chat/stream", {
+            const apiUrl = process.env.NEXT_PUBLIC_API_URL || "http://localhost:8000/api/v1";
+            const response = await fetch(`${apiUrl}/chat/stream`, {
                 method: "POST",
                 headers: { "Content-Type": "application/json" },
                 body: JSON.stringify({ message: fullMessage, history }) // Send ID-enriched message