fix: propagate _SETUP variable through unified layout system

- Add _SETUP to globals import list in renderUnifiedLayoutHeader/Footer
- Pass _SETUP via $vars in setup.php render calls
- Set $GLOBALS['_SETUP'] explicitly in setup.php
- Make header.php theme check null-safe (defensive against missing
  $rUserInfo/$rThemes on setup page)

src/public/Views/admin/header.php

@@ -33,7 +33,7 @@
         <link href="assets/css/icons.css" rel="stylesheet" type="text/css" />
         <link href="assets/libs/jquery-vectormap/jquery-jvectormap-1.2.2.css" rel="stylesheet" type="text/css" />
         <link href="assets/libs/bootstrap-colorpicker/bootstrap-colorpicker.min.css" rel="stylesheet" type="text/css" />
-        <?php if (isset($_SETUP) || !$rThemes[$rUserInfo['theme']]['dark']): ?>
+        <?php if (!empty($_SETUP) || !($rThemes[$rUserInfo['theme'] ?? ''] ?? ['dark' => false])['dark']): ?>
             <link href="assets/css/bootstrap.css" rel="stylesheet" type="text/css" />
             <link href="assets/css/app.css" rel="stylesheet" type="text/css" />
             <link href="assets/css/listings.css" rel="stylesheet" type="text/css" />

src/public/Views/admin/setup.php

@@ -132,8 +132,9 @@ if (!isset(RequestManager::getAll()['update'])):
 
     $_TITLE = 'Database Migration';
     $_SETUP = true;
+    $GLOBALS['_SETUP'] = true;
     require_once __DIR__ . '/../layouts/admin.php';
-    renderUnifiedLayoutHeader('admin');
+    renderUnifiedLayoutHeader('admin', ['_SETUP' => true]);
 ?>
     <div class="wrapper boxed-layout" <?php if (empty($_SERVER['HTTP_X_REQUESTED_WITH']) || strtolower($_SERVER['HTTP_X_REQUESTED_WITH']) != 'xmlhttprequest') {
                                         } else {
@@ -302,7 +303,7 @@ if (!isset(RequestManager::getAll()['update'])):
     </div>
     <?php
     require_once __DIR__ . '/../layouts/footer.php';
-    renderUnifiedLayoutFooter('admin');
+    renderUnifiedLayoutFooter('admin', ['_SETUP' => true]);
     ?>
     <?php if ($rMigrating): ?>
         <script>

src/public/Views/layouts/admin.php

@@ -29,7 +29,7 @@ if (!function_exists('renderUnifiedLayoutHeader')) {
             'rUserInfo', 'rSettings', 'rThemes', 'rMobile', 'rHues',
             'db', 'language', 'allServersHealthy', 'rServerError',
             'rServers', 'allServers', 'rUpdate', '_TITLE', 'rModal',
-            'rProxyServers', 'rPermissions', '_PAGE',
+            'rProxyServers', 'rPermissions', '_PAGE', '_SETUP',
         ] as $_g) {
             if (array_key_exists($_g, $GLOBALS)) {
                 $$_g = $GLOBALS[$_g];

src/public/Views/layouts/footer.php

@@ -28,7 +28,7 @@ if (!function_exists('renderUnifiedLayoutFooter')) {
             'rUserInfo', 'rSettings', 'rThemes', 'rMobile', 'rHues',
             'db', 'language', 'rServers', 'allServers', 'rUpdate',
             '_TITLE', 'rModal', 'rProxyServers', 'rPermissions',
-            'rServerError', 'allServersHealthy', '_PAGE',
+            'rServerError', 'allServersHealthy', '_PAGE', '_SETUP',
             'rStreamIDs', 'rFilterBy', 'rSortArray', 'rFilterArray',
             'rSearchBy', 'rURLs', 'rSubtitles', 'rLegacy', 'rSeries',
             'rYearStart', 'rYearEnd', 'rRatingStart', 'rRatingEnd',