webui: create the secret drop at install, not by hand

libreportal-ownership gained secret-dir, and nothing called it. I made the
directory by hand while building the channel, which hid that a fresh install
would not have one — /api/setup/secret answers 503 without it, so a remote
backup destination could not be added at all.

Created alongside webui-bind, which is its mirror and needs root for the same
reason: ownership only root can set, in place before anyone types a password
into the wizard.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

scripts/function/permission/libreportal_folders.sh

@@ -83,6 +83,12 @@ reconcileWebuiDirOwnership()
     fi
     runOwnership webui
     runOwnership webui-bind
+    # The drop the WebUI hands secrets through, created here for the same reason
+    # webui-bind is: it needs ownership only root can set, and it has to exist
+    # before the first time someone types a password into the wizard. Without
+    # it /api/setup/secret answers 503 and a remote backup destination cannot be
+    # added at all.
+    runOwnership secret-dir
     isSuccessful "Reconciled WebUI dir ($webui_dir)"
 }