fix: normalize aliasUrl to absolute URL before storing alsoKnownAs

Without https://, jsonld rejects the value as a relative object
reference during signature verification, breaking Mastodon migration.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

lib/controllers/migrate.js

@@ -42,7 +42,11 @@ export function migratePostController(mountPath, pluginOptions) {
       const profileCollection = application?.collections?.get("ap_profile");
       let result = null;
 
-      const aliasUrl = request.body.aliasUrl?.trim();
+      let aliasUrl = request.body.aliasUrl?.trim();
+      // Ensure aliasUrl is an absolute URL — prepend https:// if missing scheme
+      if (aliasUrl && !/^https?:\/\//i.test(aliasUrl)) {
+        aliasUrl = `https://${aliasUrl}`;
+      }
       const submittedAliasField = Object.prototype.hasOwnProperty.call(
         request.body || {},
         "aliasUrl",