fix: unblock add-node API and improve online status detection

Co-authored-by: Cursor <cursoragent@cursor.com>

panel/app.py

@@ -97,7 +97,7 @@ def login_required(view):
     return wrapped
 
 
-def apply_singbox() -> tuple[bool, str]:
+def render_singbox_config() -> tuple[bool, str]:
     env = os.environ.copy()
     env["JIEDIAN_ROOT"] = str(ROOT)
     proc = subprocess.run(
@@ -108,9 +108,23 @@ def apply_singbox() -> tuple[bool, str]:
     )
     if proc.returncode != 0:
         return False, proc.stderr or proc.stdout or "配置生成失败"
-    restart = subprocess.run(["systemctl", "restart", "sing-box"], capture_output=True, text=True)
-    if restart.returncode != 0:
-        return False, restart.stderr or restart.stdout or "sing-box 重启失败"
+    return True, "ok"
+
+
+def restart_singbox_async() -> None:
+    """后台重启 sing-box，避免添加/删除节点 API 长时间阻塞。"""
+    subprocess.Popen(
+        ["systemctl", "restart", "sing-box"],
+        stdout=subprocess.DEVNULL,
+        stderr=subprocess.DEVNULL,
+    )
+
+
+def apply_singbox() -> tuple[bool, str]:
+    ok, msg = render_singbox_config()
+    if not ok:
+        return False, msg
+    restart_singbox_async()
     return True, "ok"