fix(captcha): wire scene switches and rename menu to 人机验证

- Admin: 登录权限 → 人机验证; 停用场景 → 启用场景 (opt-in)
- Normalize enabled_scenarios with legacy disabled_scenarios BC
- Sign-in: never soft-bypass captcha; cancel unlocks button
- Captcha JS: cancel path finishes pending callback as false

assets/js/credits.js

@@ -114,14 +114,28 @@
 			} catch (_) {}
 		}
 
-		function triggerCaptcha(callback) {
+		function triggerCaptcha(onSuccess, onFail) {
+			var mount = document.querySelector('[data-signin-captcha]');
 			var state = window.AKSRTCaptchaState;
 			var scene = state && state.scenes && state.scenes.signin;
+
 			if (scene && typeof scene.verify === 'function') {
-				scene.verify(callback);
+				scene.verify(function (ok) {
+					if (ok === false) {
+						if (typeof onFail === 'function') onFail('已取消验证');
+						return;
+					}
+					onSuccess();
+				});
 				return;
 			}
-			callback();
+
+			if (mount) {
+				if (typeof onFail === 'function') onFail('人机验证加载中，请稍候再试');
+				return;
+			}
+
+			onSuccess();
 		}
 
 		btn.addEventListener('click', function () {
@@ -129,19 +143,13 @@
 			btn.innerHTML = '…';
 			setTip('');
 
-			var captchaDone = false;
-			var timeoutId = setTimeout(function () {
-				if (!captchaDone) {
-					captchaDone = true;
-					doSignin();
-				}
-			}, 30000);
-
 			triggerCaptcha(function () {
-				clearTimeout(timeoutId);
-				if (captchaDone) return;
-				captchaDone = true;
 				doSignin();
+			}, function (msg) {
+				resetCaptcha();
+				if (msg) setTip(msg);
+				btn.disabled = false;
+				btn.innerHTML = '签到';
 			});
 
 			function doSignin() {