fix theme editor radio buttons: accessibility and double dots

Wrap logo mode radios in fieldset/legend for screen reader grouping.
Hide native radio input properly (was using nonexistent .hidden class),
add aria-hidden on decorative dot spans, focus-visible ring on cards,
and IDs on each input.

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

assets/css/admin/components.css

@@ -4024,7 +4024,14 @@
 }
 
 /* Radio card selector (logo mode picker) */
+.theme-radio-fieldset {
+  border: none;
+  padding: 0;
+  margin: 0;
+}
+
 .theme-radio-card {
+  position: relative;
   display: flex;
   align-items: center;
   gap: 0.75rem;
@@ -4037,6 +4044,17 @@
   &:hover {
     border-color: var(--admin-text-ghost);
   }
+
+  &:has(:focus-visible) {
+    outline: 2px solid var(--t-accent);
+    outline-offset: 2px;
+  }
+}
+
+.theme-radio-input {
+  position: absolute;
+  opacity: 0;
+  pointer-events: none;
 }
 
 .theme-radio-card-active {