feat(auth): support bot-managed messenger login flow

src/server.js

@@ -90,6 +90,7 @@ app.post('/bot/messenger-login', async (req, res) => {
   const userId = String(req.body?.userId || '').trim();
   const email = String(req.body?.email || '').trim().toLowerCase();
   const channelId = String(req.body?.channelId || '').trim();
+  const skipDispatch = req.body?.skipDispatch === true;
   if (!channelId || (!userId && !email)) {
     res.status(400).json({ error: 'channelId and (userId or email) are required.' });
     return;
@@ -140,6 +141,7 @@ app.post('/bot/messenger-login', async (req, res) => {
   ).replace(/\/$/, '');
   const loginUrl = `${frontendUrl}/login?login_token=${encodeURIComponent(login.loginToken)}`;
 
+  if (!skipDispatch) {
     const dispatch = await sendMessengerMessage({
       type: channel,
       channelId,
@@ -152,6 +154,7 @@ app.post('/bot/messenger-login', async (req, res) => {
       res.status(502).json({ error: dispatch.detail });
       return;
     }
+  }
 
   res.json({
     ok: true,