feat(chat): Implement real-time SSE streaming with reasoning steps and improved UI indicators.

frontend/src/App.tsx

@@ -4,7 +4,9 @@ import { MainLayout } from "./components/layout/MainLayout"
 import { LoginForm } from "./components/auth/LoginForm"
 import { RegisterForm } from "./components/auth/RegisterForm"
 import { AuthCallback } from "./components/auth/AuthCallback"
+import { ChatInterface } from "./components/chat/ChatInterface"
 import { AuthService, type UserResponse } from "./services/auth"
+import { ChatService } from "./services/chat"
 import { registerUnauthorizedCallback } from "./services/api"
 
 function App() {
@@ -12,6 +14,7 @@ function App() {
   const [user, setUser] = useState<UserResponse | null>(null)
   const [authMode, setAuthMode] = useState<"login" | "register">("login")
   const [isLoading, setIsLoading] = useState(true)
+  const [selectedThreadId, setSelectedThreadId] = useState<string | null>(null)
 
   useEffect(() => {
     // Register callback to handle session expiration from anywhere in the app
@@ -55,6 +58,17 @@ function App() {
     } finally {
       setIsAuthenticated(false)
       setUser(null)
+      setSelectedThreadId(null)
+    }
+  }
+
+  const handleCreateTempChat = async () => {
+    try {
+      const conv = await ChatService.createConversation("Temporary Chat")
+      setSelectedThreadId(conv.id)
+    } catch (err) {
+      console.error("Failed to create conversation:", err)
+      alert("Failed to start chat session. Please try again.")
     }
   }
 
@@ -88,13 +102,12 @@ function App() {
             </div>
           ) : (
             <MainLayout>
-              <div className="flex flex-col gap-4">
-                <div className="flex justify-between items-center">
+              <div className="flex flex-col h-full gap-4">
+                <div className="flex justify-between items-center shrink-0">
                   <div>
-                    <h1 className="text-2xl font-bold">
+                    <h1 className="text-xl font-bold">
                       Welcome, {user?.display_name || user?.email || "User"}!
                     </h1>
-                    <p className="text-sm text-muted-foreground">{user?.email}</p>
                   </div>
                   <button
                     onClick={handleLogout}
@@ -103,9 +116,43 @@ function App() {
                     Logout
                   </button>
                 </div>
-                <p className="text-muted-foreground mt-4">
-                  Select a conversation from the sidebar or start a new one to begin your analysis.
-                </p>
+                
+                <div className="flex-1 min-h-0">
+                  {selectedThreadId ? (
+                    <ChatInterface threadId={selectedThreadId} />
+                  ) : (
+                    <div className="flex flex-col items-center justify-center h-full text-center space-y-4 bg-muted/30 rounded-xl border border-dashed p-12">
+                      <div className="p-4 bg-background rounded-full shadow-sm">
+                        <svg
+                          className="w-12 h-12 text-primary"
+                          fill="none"
+                          stroke="currentColor"
+                          viewBox="0 0 24 24"
+                          xmlns="http://www.w3.org/2000/svg"
+                        >
+                          <path
+                            strokeLinecap="round"
+                            strokeLinejoin="round"
+                            strokeWidth={2}
+                            d="M8 10h.01M12 10h.01M16 10h.01M9 16H5a2 2 0 01-2-2V6a2 2 0 012-2h14a2 2 0 012 2v8a2 2 0 01-2 2h-5l-5 5v-5z"
+                          />
+                        </svg>
+                      </div>
+                      <div className="max-w-xs space-y-2">
+                        <h2 className="text-lg font-semibold">Ready to analyze election data?</h2>
+                        <p className="text-sm text-muted-foreground">
+                          Create a new conversation in the sidebar to start asking questions.
+                        </p>
+                        <button 
+                          onClick={handleCreateTempChat}
+                          className="mt-4 px-4 py-2 bg-primary text-primary-foreground rounded-md text-sm font-medium hover:bg-primary/90"
+                        >
+                          Start Temporary Chat
+                        </button>
+                      </div>
+                    </div>
+                  )}
+                </div>
               </div>
             </MainLayout>
           )