feat(badges): dual-read/write wear_medal alias + default wear

Align badge wear meta with zibll and auto-pick first owned badge.

src/AKSRT/User/Badges.php

@@ -185,9 +185,14 @@ class Badges {
 		}
 		$wear = sanitize_key((string) get_user_meta($user_id, self::META_WEAR, true));
 		if ($wear === '') {
-			return '';
+			// zibll alias.
+			$wear = sanitize_key((string) get_user_meta($user_id, 'wear_medal', true));
 		}
 		$owned = self::get_owned($user_id);
+		if ($wear === '') {
+			// Default to newest/first owned badge when unset (zibll behavior).
+			return $owned[0] ?? '';
+		}
 		return in_array($wear, $owned, true) ? $wear : '';
 	}
 
@@ -211,6 +216,7 @@ class Badges {
 			return new \WP_Error('aksrt_badge_not_owned', __('尚未获得该徽章', 'aksrt'), ['status' => 403]);
 		}
 		update_user_meta($user_id, self::META_WEAR, $slug);
+		update_user_meta($user_id, 'wear_medal', $slug); // zibll alias
 		return true;
 	}