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>

CHANGELOG.md

@@ -2,6 +2,13 @@
 
 All notable changes to this project will be documented in this file.
 
+## [1.0.9] - 2026-02-19
+
+### Performance
+
+- **Color variation CSS transient caching** (`functions.php`): `wp_bootstrap_variation_colors()` now caches the generated inline CSS in a 24-hour WordPress transient keyed by `wp_bootstrap_variation_css_` + an MD5 of the active stylesheet slug. Previously the palette iteration and CSS string building ran on every frontend page load. The transient is immediately invalidated on `switch_theme` and `save_post_wp_global_styles`, so changes made via the Design Editor are reflected instantly.
+- **Twig template recompilation gated behind `WP_DEBUG`** (`inc/Twig/TwigService.php`): `auto_reload` in the Twig `Environment` constructor was hardcoded to `true`, causing Twig to stat every compiled template file on every request to check for source changes. Changed to `WP_DEBUG` so template recompilation only occurs during development. In production (`WP_DEBUG = false`) compiled Twig templates are served from cache without filesystem mtime checks.
+
 ## [1.0.8] - 2026-02-19
 
 ### Security