re-add auth layer

app.py

@@ -157,4 +157,12 @@ def build_app():
 
 if __name__ == "__main__":
     app = build_app()
-    app.queue(max_size=5).launch(show_api=False)
+    app.queue(max_size=5).launch(
+        show_api=False,
+        auth=[
+            (os.getenv("APP_USERNAME"), os.getenv("APP_PASSWORD")),
+            (os.getenv("APP_PUBLIC_USERNAME"), os.getenv("APP_PUBLIC_PASSWORD")),
+        ],
+        auth_message="Login to Candid's AI assistant",
+        ssr_mode=False
+    )