v0.2.0 - Design Editor: templates, patterns, header/footer variations

Full Design Editor compatibility with custom block categories, page templates,
header/footer variations, and navigation styles. Both FSE (admin) and Twig
(frontend) sides kept in sync.

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

assets/css/style.css

@@ -11911,6 +11911,19 @@ h1, .h1, h2, .h2, h3, .h3, h4, .h4, h5, .h5, h6, .h6, blockquote, caption, figca
   border-radius: 0.25rem;
 }
 
+.header-transparent {
+  position: absolute;
+  width: 100%;
+  z-index: 1030;
+}
+.header-transparent .navbar {
+  background: transparent !important;
+}
+
+[data-bs-theme=dark] .offcanvas {
+  --bs-offcanvas-bg: var(--bs-body-bg);
+}
+
 [data-bs-theme=dark] .is-style-alert-info {
   background-color: #032830;
   border-color: #055160;