feat(update): allow opting into the dev channel from a stable build

The panel version button opened the GitHub releases page on a stable, up-to-date build, and the dev-channel toggle only rendered on dev builds, so there was no in-panel path from stable to dev. Drop the IsDevBuild() guard in devChannelActive (the toggle alone drives the channel now), always open the update modal instead of releases, and always render the Dev channel switch.

frontend/src/pages/index/IndexPage.tsx

@@ -66,7 +66,6 @@ export default function IndexPage() {
   useEffect(() => { setMessageInstance(messageApi); }, [messageApi]);
 
   const [accessLogEnable, setAccessLogEnable] = useState(false);
-  const [isDevBuild, setIsDevBuild] = useState(false);
   const [devChannelEnable, setDevChannelEnable] = useState(false);
   const [panelUpdateInfo, setPanelUpdateInfo] = useState<PanelUpdateInfo>({
     currentVersion: '',
@@ -90,12 +89,11 @@ export default function IndexPage() {
   const [loadingTip, setLoadingTip] = useState(t('loading'));
 
   useEffect(() => {
-    HttpUtil.post<{ accessLogEnable?: boolean; isDevBuild?: boolean; devChannelEnable?: boolean }>(
+    HttpUtil.post<{ accessLogEnable?: boolean; devChannelEnable?: boolean }>(
       '/panel/api/setting/defaultSettings',
     ).then((msg) => {
       if (msg?.success && msg.obj) {
         setAccessLogEnable(!!msg.obj.accessLogEnable);
-        setIsDevBuild(!!msg.obj.isDevBuild);
         setDevChannelEnable(!!msg.obj.devChannelEnable);
       }
     });
@@ -128,11 +126,7 @@ export default function IndexPage() {
   }, [refresh]);
 
   function openPanelVersion() {
-    if (panelUpdateInfo.updateAvailable || isDevBuild) {
-      setPanelUpdateOpen(true);
-    } else {
-      window.open('https://github.com/MHSanaei/3x-ui/releases', '_blank', 'noopener,noreferrer');
-    }
+    setPanelUpdateOpen(true);
   }
 
   async function handleChannelChange(dev: boolean) {
@@ -463,7 +457,6 @@ export default function IndexPage() {
           <PanelUpdateModal
             open={panelUpdateOpen}
             info={panelUpdateInfo}
-            isDevBuild={isDevBuild}
             devChannelEnable={devChannelEnable}
             onChannelChange={handleChannelChange}
             onClose={() => setPanelUpdateOpen(false)}

frontend/src/pages/index/PanelUpdateModal.tsx

@@ -25,7 +25,6 @@ interface BusyEvent {
 interface PanelUpdateModalProps {
   open: boolean;
   info: PanelUpdateInfo;
-  isDevBuild?: boolean;
   devChannelEnable?: boolean;
   onChannelChange?: (dev: boolean) => void | Promise<void>;
   onClose: () => void;
@@ -35,7 +34,6 @@ interface PanelUpdateModalProps {
 export default function PanelUpdateModal({
   open,
   info,
-  isDevBuild,
   devChannelEnable,
   onChannelChange,
   onClose,
@@ -113,18 +111,16 @@ export default function PanelUpdateModal({
           />
         )}
 
-        {isDevBuild && (
-          <div className="version-list">
-            <div className="version-list-item">
-              <span>{t('pages.index.devChannel')}</span>
-              <Switch
-                checked={!!devChannelEnable}
-                loading={channelBusy}
-                onChange={handleChannel}
-              />
-            </div>
+        <div className="version-list">
+          <div className="version-list-item">
+            <span>{t('pages.index.devChannel')}</span>
+            <Switch
+              checked={!!devChannelEnable}
+              loading={channelBusy}
+              onChange={handleChannel}
+            />
           </div>
-        )}
+        </div>
 
         {devChannelEnable && (
           <Alert