refactor: update authentication mechanism for Gradio app launch

app.py

@@ -4,10 +4,12 @@ import gradio as gr
 from core import RAG, parse_cas_input
 
 rag = RAG()
-
-DEMO_USER = os.getenv("USERNAME", "demo")
-DEMO_PASS = os.getenv("PASSWORD", "chemical2026")
-
+auth_list = []
+auth_env = os.getenv("AUTH_USERS", "")
+for pair in auth_env.split(","):
+    if ":" in pair:
+        user, pwd = pair.split(":", 1)
+        auth_list.append((user.strip(), pwd.strip()))
 EXAMPLE_INPUTS = [
     "7664-39-3",
     "7664-39-3, 128-37-0",
@@ -127,4 +129,4 @@ with gr.Blocks(
             )
 
 if __name__ == "__main__":
-    demo.launch(auth=(DEMO_USER, DEMO_PASS))
+    demo.launch(auth=auth_list)