[grade=B] feat(auth): onboard missing credentials into encrypted vault

dashcaddy-api/src/utilities/middleware.js

@@ -330,17 +330,22 @@ module.exports = function configureMiddleware(app, {
   const ssoHandoffTokens = new Map();
   const SSO_HANDOFF_TTL_MS = 60 * 1000;
 
-  function createHandoffToken() {
+  function createHandoffToken(expectedHost = null) {
     const token = crypto.randomBytes(24).toString('base64url');
-    ssoHandoffTokens.set(token, { exp: Date.now() + SSO_HANDOFF_TTL_MS });
+    ssoHandoffTokens.set(token, {
+      exp: Date.now() + SSO_HANDOFF_TTL_MS,
+      expectedHost: expectedHost ? String(expectedHost).toLowerCase() : null,
+    });
     return token;
   }
 
-  function redeemHandoffToken(token) {
+  function redeemHandoffToken(token, actualHost = null) {
     if (!token) return false;
     const entry = ssoHandoffTokens.get(token);
     ssoHandoffTokens.delete(token); // one-time use regardless of outcome
-    return !!entry && entry.exp > Date.now();
+    if (!entry || entry.exp <= Date.now()) return false;
+    if (!entry.expectedHost) return true;
+    return !!actualHost && entry.expectedHost === String(actualHost).toLowerCase();
   }
 
   function setHostOnlySessionCookie(res, durationKey) {