feat: implement council v3 round-table mode

app.py

@@ -107,17 +107,35 @@ if "research_steps_output" not in st.session_state:
 with st.sidebar:
     st.header("⚙️ 设置")
     
-    # 全局 API Key 设置
-    with st.expander("🔑 API Key 设置", expanded=True):
-        use_custom_key = st.checkbox("使用自定义 API Key")
-        if use_custom_key:
-            api_key = st.text_input(
-                "API Key",
-                type="password",
-                help="留空则使用环境变量中的 Key"
+    # 全局 API Key & Provider 设置
+    with st.expander("🔑 API / Provider 设置", expanded=True):
+        # Provider Selection
+        selected_provider_label = st.selectbox(
+            "选择 API 提供商",
+            options=list(config.LLM_PROVIDERS.keys()),
+            index=0
         )
-        else:
-            api_key = DEFAULT_API_KEY
+        
+        provider_config = config.LLM_PROVIDERS[selected_provider_label]
+        provider_id = selected_provider_label.lower() 
+        
+        # API Key Input
+        default_key = os.getenv(provider_config["api_key_var"], "")
+        api_key = st.text_input(
+            f"{selected_provider_label} API Key", 
+            type="password", 
+            value=default_key,
+            help=f"环境变量: {provider_config['api_key_var']}"
+        )
+        
+        # Base URL
+        base_url = st.text_input(
+            "API Base URL", 
+            value=provider_config["base_url"]
+        )
+            
+        if not api_key:
+            st.warning("请配置 API Key 以继续")
             
     st.divider()