perf: color variation CSS transient caching and Twig auto_reload fix (v1.0.9)

- functions.php: cache wp_bootstrap_variation_colors() output in a 24-hour
  transient keyed by md5(get_stylesheet()); invalidate on switch_theme and
  save_post_wp_global_styles so Design Editor changes apply immediately
- TwigService.php: change auto_reload from hardcoded true to WP_DEBUG so
  Twig stops stat()-ing compiled template files on every production request

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

inc/Twig/TwigService.php

@@ -25,9 +25,9 @@ class TwigService
 
         $loader = new FilesystemLoader($viewsDir);
         $this->twig = new Environment($loader, [
-            'cache' => WP_DEBUG ? false : $cacheDir,
-            'debug' => WP_DEBUG,
-            'auto_reload' => true,
+            'cache'        => WP_DEBUG ? false : $cacheDir,
+            'debug'        => WP_DEBUG,
+            'auto_reload'  => WP_DEBUG,
         ]);
 
         $this->registerWordPressFunctions();